research summary vs abstract

Summary vs. Abstract: What's the Difference?

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What is the difference between Abstract, conclusion and summary?

The above question is self explanatory, still I would like to break it into two parts.

Q1. What is the difference between abstract and summary/conclusion?

Q2. What is the difference between summary and conclusion ?

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• 27 Sadly, a lot of today's abstracts and conclusions read as: Abstract: "In this paper, we will show X using data Y and study Z", Conclusions: "In this paper, we showed X to study Z using data Y" — i.e., more often than not, the only difference is in the tense of the passage. –  user6431 Commented Apr 11, 2013 at 22:12
• 7 See classic texts K. K. Landes. A scrutiny of the abstract. Bulletin of the American Meteorological Society, 50(9):1992, 1969. and J. F. Claerbout. A scrutiny of the introduction. Stanford Exploration Project, 59:287 – 291, 1988. –  mankoff Commented Apr 11, 2013 at 22:37
• 1 some links: ece.utep.edu/courses/ee3329/ee3329/abstract.html and aapg.org/bulletin/abstract_scrutiny.pdf –  JRN Commented Apr 12, 2013 at 22:28
• 9 See How to write a paper . Here's a choice excerpt: There are papers that may benefit from a conclusion section, but they are relatively few (say, less than 5% of the papers). Certainly, the inclusion of a conclusion section should not be the default. –  David Ketcheson Commented Dec 6, 2013 at 4:35
• 2 Tell them what you're going to tell them. Tell them. Tell them what you told them. –  Austin Henley Commented Mar 12, 2016 at 5:26

8 Answers 8

The abstract is written for the potentially interested reader. While writing it, keep in mind that most readers read the abstract before they read the paper (sounds obvious, but many abstracts read like the authors did not consider this). The abstract should give an impression of what the paper will be about. Do not use jargon or any abbreviations here. It should be understandable for non-specialists and even for people from fields somehow far away.

The conclusion should conclude the paper and is written for the reader who already has read the paper. In other words: most readers have read the paper when they read the conclusion. Again, this sounds obvious but, again, a lot of conclusions do not read like this. It does not make sense to write a conclusion like "we have shown this and that by using this and that method". Well, this is what the reader has just read (and what he may know since he has read the abstract). A proper conclusion should tell the reader what she can or he could do with the newly acquired knowledge. Answer the question "So what?".

A summary sums up the paper. I am not sure if a paper needs a summary.

I've written some tips for abstracts some time ago:

• Avoid jargon. Although this sounds obvious, most abstracts contain jargon in one way or the other. Of course one can not avoid the use of specific terminology and technical terms but even then there is an easy check if a technical term is appropriate: Try to find a definition on the internet (if the term has a fairly stable wikipedia page, there it is not jargon) – if you do not succeed within a few minutes you should find a different word.
• Use buzzwords. This may sound to contradict the previous point and in part it does. But note that you can use a buzzword together with its explanation. Again, the example from the previous point works: “Funk metric” may be a buzzword and the explanation using the name “Finsler” is supposed to ring a bell (as I learned, it is related to Hilbert’s 23rd problem). This helps the readers to find related work and to remember what was the field you were working in.
• General to specific. In general, it’s good advice to work from general to specific. Start with a sentence which points in the direction of the field you are working in. So your potential audience will know from the beginning in which field your work is situated.
• Answer questions. If you think that your work answers questions, why not pose the questions in the abstract? This may motivate the readers to think by themselves and draw their interest to the topic.
• Don’t be afraid of layman’s terms. Although layman’s terms usually do not give exact description and sometimes even are ridiculously oversimplified, they still help to form a mental picture.

• 2 Just to add a little on this, abstracts should be short (1/2 page in my field) and should try to explain all of the key points of the paper, including the methodology, key findings, implications, etc. The goal of the abstract is to let the reader decide if there is any value in reading the entire paper. –  earthling Commented Apr 11, 2013 at 23:09
• 4 For abstracts, I always follow the advice in Simon Peyton Jones's presentation " How to write a great research paper " (He credits Kent Beck, but I can't find the exact reference): 1. State the problem 2. Say why it's an interesting problem 3. Say what your solution achieves 4. Say what follows from your solution. It's amazing how much clearer and to the point your abstracts become. –  ThomasH Commented Apr 15, 2013 at 19:22
• 4 I downvoted because, for technical fields, using jargon in the abstract is almost always a good thing. Show me a mathematics abstract with no "jargon". But you should avoid using terms that your intended audience will not already know. –  David Ketcheson Commented Dec 6, 2013 at 4:38
• 2 'It does not make sense to write a conclusion like "we have shown this and that by using this and that method"' - I somewhat disagree here. The reader has read the details of the paper before reading the conclusion (or maybe not even that, if they follow the abstract - conclusion - rest of text method of approaching an unknown paper), but especially due to this large amount of information, it is important that the conclusion briefly summarizes the key content in a few sentences. Cf. with presentation slides, where the last slide summarizes the key points. –  O. R. Mapper Commented Dec 10, 2015 at 12:35
• 1 Yes, this. The difference between the abstract and the conclusion is in the intended audience. A caveat is that many readers will skip to the conclusion to get an idea of what they will know after reading the paper. But you still write the conclusion as if to an audience that has already read it. –  Caleb Stanford Commented Oct 19, 2017 at 14:08

A1 : In the context of a journal article, thesis etc., the abstract should provide a brief summary of each of the main parts of the article: Introduction, Methods, Results and Discussion. In the words of Houghton (1975), "An abstract can be defined as a summary of the information in a document". The Conclusions (in some cases also called a Summary ) chapter is a summary of the main ideas that come out from the discussion (e.g., Katz, 2009) and hence only a subset of the abstract. Usually, the Conclusions sum up the discussion whereas the abstract only reiterates the most important of the conclusions.

A2 : The difference between a summary and the conclusions is less clear. First, it is not clear if the summary is to be compared with the Abstract or the Conclusions. A summary may also be more appropriate as Conclusions when writing an overview where the conclusions may not be easy to identify. As stated above some journals use the word Summary instead of Conclusions . Sometimes this can also be labelled Synthesis and cap off a lengthy discussion.

References:

Houghton, B., 1975. Scientific periodicals: their historical development, characteristics and control. Hamden CT, Shoe String Press.

Katz, M.J., 2009. From research to manuscript. A guide to scientific writing. Second edition. Berlin, Springer.

• 7 I don't think it's accurate to say that the conclusion is a subset of the abstract. Some elements from the abstract make it into the conclusion, but the conclusion will likely include information not in the abstract as well, such as a detailed discussion of "why it all matters". –  Irwin Commented Apr 12, 2013 at 18:20
• @Peter Jansson Regarding the conclusions you mentioned ".... and hence only a subset of the abstract". Then you mentioned: ".... the abstract only reiterates the most important of the conclusions." How it comes? –  AlFagera Commented Jul 15, 2019 at 15:06

A conclusion section might for example include speculations about some patterns in the data, or proposals for future research. It basically is really the only place to put your opinions. A summary I expect would not include any opinions and just re-iterate the findings and weaknesses in the study.

As the other answer mentioned, the abstract should include all the main aspects of the paper in an abbreviated form - the topic, the hypotheses, the participants and study design, and the results.

Abstract: Author short story about what is in it (no matter good or bad, valuable or scrap) Conclusion: Authors statement about the findings justified by the detailed content (findings/achievement/affirmation of a doubtful fact/negation of an established belief...etc) for a reader who has a guided-travel across by the author.

abstract = what is to be done by researcher in the given paper.

summary = what is accomplished in the paper under consideration.

conclusion = what are the limitations of study, what needs to be done by upcoming researchers.

• 1 I am not sure about the equal sign you use. I have seen papers using conclusion for summary and vice versa. –  Nobody Commented Jan 4, 2016 at 14:39

Summary: Its a brief note that gives us an overview, ideas and insight about major topics in a paper.

Abstract: Its a short note that express the contents of the work.

Conclusion: Its a statement/decision reached by the researcher based on findings in the research.

One basic difference: An abstract is always at the beginning of a academic paper. A conclusion is always at the end. A summary could be anywhere, even separate from the paper itself, so it's a bit more slippery.

• The abstract is like a movie trailer.
• The summary is an arrangement of actions/events of movie in a short way.
• The conclusion is the objective of the movie in light of the evidence and arguments given in the movie.

The conclusion of one person can vary from that of another.

• 2 Now, the question becomes what is the difference between movie trailor and summary? –  Nobody Commented Dec 10, 2015 at 11:11
• 2 You could go so much further with this analogy. E.g., summary and conclusion together are like a review of a movie, with the summary being, well, the summary and the conclusion the interpretation and rating. –  Wrzlprmft ♦ Commented Dec 10, 2015 at 12:05
• The abstract might very well be completely separate. –  vonbrand Commented Jan 4, 2016 at 14:29

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What’s the Difference Between an Abstract, Summary, and Annotation?

With so many different terms related to citations (e.g. MLA format , footnotes, abstract, etc.), it can be difficult to understand how each one could fit into your paper. Let’s take a look at a few of the most commonly confused citation terms, and ways that you can properly use them in your work.

What is an Abstract? When do I use it?

An abstract is a condensed overview of a paper that usually includes the purpose of the paper/research study, the basic design of the study, the major findings, and a brief summary of your interpretations of the conclusions. Abstracts are usually used in social science or scientific papers, and are generally 300 words or less.

What is a Summary? When do I use it?

Like an abstract, a summary is just a condensed write-up on the topic discussed in your paper. However, summaries are more open ended than abstracts, and can contain much more varied information. They can be included in virtually any type of paper, and do not have a specific word count limit. Always check with your instructor for those types of guidelines before handing in your summary and paper.

What is an Annotation? When do I use it?

Annotations, otherwise referred to as annotated bibliographies, are contextual blurbs that are placed underneath the citation that they refer to within the bibliography of a paper. Each annotation is usually about 150 words, and is a descriptive and evaluative paragraph. The purpose of the annotation is to inform the reader of the relevance, accuracy, and quality of each source cited.

Before including any of these options in your paper, be sure to check with your instructor about their specifications for your assignment. It might also be beneficial to run it through a grammar checker in case there are any errors you may have missed in the abstract, summary, or annotation. —

If you need to create APA citations , learn how to cite a book , or are looking to for a way to review your paper, try BibMe Plus’s plagiarism and grammar checker.

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Writing an Abstract for Your Research Paper

Definition and Purpose of Abstracts

An abstract is a short summary of your (published or unpublished) research paper, usually about a paragraph (c. 6-7 sentences, 150-250 words) long. A well-written abstract serves multiple purposes:

• an abstract lets readers get the gist or essence of your paper or article quickly, in order to decide whether to read the full paper;
• an abstract prepares readers to follow the detailed information, analyses, and arguments in your full paper;
• and, later, an abstract helps readers remember key points from your paper.

It’s also worth remembering that search engines and bibliographic databases use abstracts, as well as the title, to identify key terms for indexing your published paper. So what you include in your abstract and in your title are crucial for helping other researchers find your paper or article.

If you are writing an abstract for a course paper, your professor may give you specific guidelines for what to include and how to organize your abstract. Similarly, academic journals often have specific requirements for abstracts. So in addition to following the advice on this page, you should be sure to look for and follow any guidelines from the course or journal you’re writing for.

The Contents of an Abstract

Abstracts contain most of the following kinds of information in brief form. The body of your paper will, of course, develop and explain these ideas much more fully. As you will see in the samples below, the proportion of your abstract that you devote to each kind of information—and the sequence of that information—will vary, depending on the nature and genre of the paper that you are summarizing in your abstract. And in some cases, some of this information is implied, rather than stated explicitly. The Publication Manual of the American Psychological Association , which is widely used in the social sciences, gives specific guidelines for what to include in the abstract for different kinds of papers—for empirical studies, literature reviews or meta-analyses, theoretical papers, methodological papers, and case studies.

Here are the typical kinds of information found in most abstracts:

• the context or background information for your research; the general topic under study; the specific topic of your research
• the central questions or statement of the problem your research addresses
• what’s already known about this question, what previous research has done or shown
• the main reason(s) , the exigency, the rationale , the goals for your research—Why is it important to address these questions? Are you, for example, examining a new topic? Why is that topic worth examining? Are you filling a gap in previous research? Applying new methods to take a fresh look at existing ideas or data? Resolving a dispute within the literature in your field? . . .
• your research and/or analytical methods
• your main findings , results , or arguments
• the significance or implications of your findings or arguments.

Your abstract should be intelligible on its own, without a reader’s having to read your entire paper. And in an abstract, you usually do not cite references—most of your abstract will describe what you have studied in your research and what you have found and what you argue in your paper. In the body of your paper, you will cite the specific literature that informs your research.

When to Write Your Abstract

Although you might be tempted to write your abstract first because it will appear as the very first part of your paper, it’s a good idea to wait to write your abstract until after you’ve drafted your full paper, so that you know what you’re summarizing.

What follows are some sample abstracts in published papers or articles, all written by faculty at UW-Madison who come from a variety of disciplines. We have annotated these samples to help you see the work that these authors are doing within their abstracts.

Choosing Verb Tenses within Your Abstract

The social science sample (Sample 1) below uses the present tense to describe general facts and interpretations that have been and are currently true, including the prevailing explanation for the social phenomenon under study. That abstract also uses the present tense to describe the methods, the findings, the arguments, and the implications of the findings from their new research study. The authors use the past tense to describe previous research.

The humanities sample (Sample 2) below uses the past tense to describe completed events in the past (the texts created in the pulp fiction industry in the 1970s and 80s) and uses the present tense to describe what is happening in those texts, to explain the significance or meaning of those texts, and to describe the arguments presented in the article.

The science samples (Samples 3 and 4) below use the past tense to describe what previous research studies have done and the research the authors have conducted, the methods they have followed, and what they have found. In their rationale or justification for their research (what remains to be done), they use the present tense. They also use the present tense to introduce their study (in Sample 3, “Here we report . . .”) and to explain the significance of their study (In Sample 3, This reprogramming . . . “provides a scalable cell source for. . .”).

Sample Abstract 1

From the social sciences.

Reporting new findings about the reasons for increasing economic homogamy among spouses

Gonalons-Pons, Pilar, and Christine R. Schwartz. “Trends in Economic Homogamy: Changes in Assortative Mating or the Division of Labor in Marriage?” Demography , vol. 54, no. 3, 2017, pp. 985-1005.

Sample Abstract 2

From the humanities.

Analyzing underground pulp fiction publications in Tanzania, this article makes an argument about the cultural significance of those publications

Emily Callaci. “Street Textuality: Socialism, Masculinity, and Urban Belonging in Tanzania’s Pulp Fiction Publishing Industry, 1975-1985.” Comparative Studies in Society and History , vol. 59, no. 1, 2017, pp. 183-210.

Sample Abstract/Summary 3

From the sciences.

Reporting a new method for reprogramming adult mouse fibroblasts into induced cardiac progenitor cells

Lalit, Pratik A., Max R. Salick, Daryl O. Nelson, Jayne M. Squirrell, Christina M. Shafer, Neel G. Patel, Imaan Saeed, Eric G. Schmuck, Yogananda S. Markandeya, Rachel Wong, Martin R. Lea, Kevin W. Eliceiri, Timothy A. Hacker, Wendy C. Crone, Michael Kyba, Daniel J. Garry, Ron Stewart, James A. Thomson, Karen M. Downs, Gary E. Lyons, and Timothy J. Kamp. “Lineage Reprogramming of Fibroblasts into Proliferative Induced Cardiac Progenitor Cells by Defined Factors.” Cell Stem Cell , vol. 18, 2016, pp. 354-367.

Sample Abstract 4, a Structured Abstract

Reporting results about the effectiveness of antibiotic therapy in managing acute bacterial sinusitis, from a rigorously controlled study

Note: This journal requires authors to organize their abstract into four specific sections, with strict word limits. Because the headings for this structured abstract are self-explanatory, we have chosen not to add annotations to this sample abstract.

Wald, Ellen R., David Nash, and Jens Eickhoff. “Effectiveness of Amoxicillin/Clavulanate Potassium in the Treatment of Acute Bacterial Sinusitis in Children.” Pediatrics , vol. 124, no. 1, 2009, pp. 9-15.

“OBJECTIVE: The role of antibiotic therapy in managing acute bacterial sinusitis (ABS) in children is controversial. The purpose of this study was to determine the effectiveness of high-dose amoxicillin/potassium clavulanate in the treatment of children diagnosed with ABS.

METHODS : This was a randomized, double-blind, placebo-controlled study. Children 1 to 10 years of age with a clinical presentation compatible with ABS were eligible for participation. Patients were stratified according to age (<6 or ≥6 years) and clinical severity and randomly assigned to receive either amoxicillin (90 mg/kg) with potassium clavulanate (6.4 mg/kg) or placebo. A symptom survey was performed on days 0, 1, 2, 3, 5, 7, 10, 20, and 30. Patients were examined on day 14. Children’s conditions were rated as cured, improved, or failed according to scoring rules.

RESULTS: Two thousand one hundred thirty-five children with respiratory complaints were screened for enrollment; 139 (6.5%) had ABS. Fifty-eight patients were enrolled, and 56 were randomly assigned. The mean age was 6630 months. Fifty (89%) patients presented with persistent symptoms, and 6 (11%) presented with nonpersistent symptoms. In 24 (43%) children, the illness was classified as mild, whereas in the remaining 32 (57%) children it was severe. Of the 28 children who received the antibiotic, 14 (50%) were cured, 4 (14%) were improved, 4(14%) experienced treatment failure, and 6 (21%) withdrew. Of the 28children who received placebo, 4 (14%) were cured, 5 (18%) improved, and 19 (68%) experienced treatment failure. Children receiving the antibiotic were more likely to be cured (50% vs 14%) and less likely to have treatment failure (14% vs 68%) than children receiving the placebo.

CONCLUSIONS : ABS is a common complication of viral upper respiratory infections. Amoxicillin/potassium clavulanate results in significantly more cures and fewer failures than placebo, according to parental report of time to resolution.” (9)

Some Excellent Advice about Writing Abstracts for Basic Science Research Papers, by Professor Adriano Aguzzi from the Institute of Neuropathology at the University of Zurich:

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• How to Write an Abstract | Steps & Examples

How to Write an Abstract | Steps & Examples

Published on February 28, 2019 by Shona McCombes . Revised on July 18, 2023 by Eoghan Ryan.

An abstract is a short summary of a longer work (such as a thesis ,  dissertation or research paper ). The abstract concisely reports the aims and outcomes of your research, so that readers know exactly what your paper is about.

Although the structure may vary slightly depending on your discipline, your abstract should describe the purpose of your work, the methods you’ve used, and the conclusions you’ve drawn.

One common way to structure your abstract is to use the IMRaD structure. This stands for:

• Introduction

Abstracts are usually around 100–300 words, but there’s often a strict word limit, so make sure to check the relevant requirements.

In a dissertation or thesis , include the abstract on a separate page, after the title page and acknowledgements but before the table of contents .

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Table of contents

Abstract example, when to write an abstract, step 1: introduction, step 2: methods, step 3: results, step 4: discussion, tips for writing an abstract, other interesting articles, frequently asked questions about abstracts.

Hover over the different parts of the abstract to see how it is constructed.

This paper examines the role of silent movies as a mode of shared experience in the US during the early twentieth century. At this time, high immigration rates resulted in a significant percentage of non-English-speaking citizens. These immigrants faced numerous economic and social obstacles, including exclusion from public entertainment and modes of discourse (newspapers, theater, radio).

Incorporating evidence from reviews, personal correspondence, and diaries, this study demonstrates that silent films were an affordable and inclusive source of entertainment. It argues for the accessible economic and representational nature of early cinema. These concerns are particularly evident in the low price of admission and in the democratic nature of the actors’ exaggerated gestures, which allowed the plots and action to be easily grasped by a diverse audience despite language barriers.

Keywords: silent movies, immigration, public discourse, entertainment, early cinema, language barriers.

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You will almost always have to include an abstract when:

• Completing a thesis or dissertation
• Submitting a research paper to an academic journal
• Writing a book or research proposal
• Applying for research grants

It’s easiest to write your abstract last, right before the proofreading stage, because it’s a summary of the work you’ve already done. Your abstract should:

• Be a self-contained text, not an excerpt from your paper
• Be fully understandable on its own
• Reflect the structure of your larger work

Start by clearly defining the purpose of your research. What practical or theoretical problem does the research respond to, or what research question did you aim to answer?

You can include some brief context on the social or academic relevance of your dissertation topic , but don’t go into detailed background information. If your abstract uses specialized terms that would be unfamiliar to the average academic reader or that have various different meanings, give a concise definition.

After identifying the problem, state the objective of your research. Use verbs like “investigate,” “test,” “analyze,” or “evaluate” to describe exactly what you set out to do.

This part of the abstract can be written in the present or past simple tense  but should never refer to the future, as the research is already complete.

• This study will investigate the relationship between coffee consumption and productivity.
• This study investigates the relationship between coffee consumption and productivity.

Next, indicate the research methods that you used to answer your question. This part should be a straightforward description of what you did in one or two sentences. It is usually written in the past simple tense, as it refers to completed actions.

• Structured interviews will be conducted with 25 participants.
• Structured interviews were conducted with 25 participants.

Don’t evaluate validity or obstacles here — the goal is not to give an account of the methodology’s strengths and weaknesses, but to give the reader a quick insight into the overall approach and procedures you used.

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Next, summarize the main research results . This part of the abstract can be in the present or past simple tense.

• Our analysis has shown a strong correlation between coffee consumption and productivity.
• Our analysis shows a strong correlation between coffee consumption and productivity.
• Our analysis showed a strong correlation between coffee consumption and productivity.

Depending on how long and complex your research is, you may not be able to include all results here. Try to highlight only the most important findings that will allow the reader to understand your conclusions.

Finally, you should discuss the main conclusions of your research : what is your answer to the problem or question? The reader should finish with a clear understanding of the central point that your research has proved or argued. Conclusions are usually written in the present simple tense.

• We concluded that coffee consumption increases productivity.
• We conclude that coffee consumption increases productivity.

If there are important limitations to your research (for example, related to your sample size or methods), you should mention them briefly in the abstract. This allows the reader to accurately assess the credibility and generalizability of your research.

If your aim was to solve a practical problem, your discussion might include recommendations for implementation. If relevant, you can briefly make suggestions for further research.

If your paper will be published, you might have to add a list of keywords at the end of the abstract. These keywords should reference the most important elements of the research to help potential readers find your paper during their own literature searches.

Be aware that some publication manuals, such as APA Style , have specific formatting requirements for these keywords.

It can be a real challenge to condense your whole work into just a couple of hundred words, but the abstract will be the first (and sometimes only) part that people read, so it’s important to get it right. These strategies can help you get started.

Read other abstracts

The best way to learn the conventions of writing an abstract in your discipline is to read other people’s. You probably already read lots of journal article abstracts while conducting your literature review —try using them as a framework for structure and style.

You can also find lots of dissertation abstract examples in thesis and dissertation databases .

Reverse outline

Not all abstracts will contain precisely the same elements. For longer works, you can write your abstract through a process of reverse outlining.

For each chapter or section, list keywords and draft one to two sentences that summarize the central point or argument. This will give you a framework of your abstract’s structure. Next, revise the sentences to make connections and show how the argument develops.

Write clearly and concisely

A good abstract is short but impactful, so make sure every word counts. Each sentence should clearly communicate one main point.

To keep your abstract or summary short and clear:

• Avoid passive sentences: Passive constructions are often unnecessarily long. You can easily make them shorter and clearer by using the active voice.
• Avoid long sentences: Substitute longer expressions for concise expressions or single words (e.g., “In order to” for “To”).
• Avoid obscure jargon: The abstract should be understandable to readers who are not familiar with your topic.
• Avoid repetition and filler words: Replace nouns with pronouns when possible and eliminate unnecessary words.
• Avoid detailed descriptions: An abstract is not expected to provide detailed definitions, background information, or discussions of other scholars’ work. Instead, include this information in the body of your thesis or paper.

If you’re struggling to edit down to the required length, you can get help from expert editors with Scribbr’s professional proofreading services or use the paraphrasing tool .

Check your formatting

If you are writing a thesis or dissertation or submitting to a journal, there are often specific formatting requirements for the abstract—make sure to check the guidelines and format your work correctly. For APA research papers you can follow the APA abstract format .

Checklist: Abstract

The word count is within the required length, or a maximum of one page.

The abstract appears after the title page and acknowledgements and before the table of contents .

I have clearly stated my research problem and objectives.

I have briefly described my methodology .

I have summarized the most important results .

I have stated my main conclusions .

I have mentioned any important limitations and recommendations.

The abstract can be understood by someone without prior knowledge of the topic.

You've written a great abstract! Use the other checklists to continue improving your thesis or dissertation.

If you want to know more about AI for academic writing, AI tools, or research bias, make sure to check out some of our other articles with explanations and examples or go directly to our tools!

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An abstract is a concise summary of an academic text (such as a journal article or dissertation ). It serves two main purposes:

• To help potential readers determine the relevance of your paper for their own research.
• To communicate your key findings to those who don’t have time to read the whole paper.

Abstracts are often indexed along with keywords on academic databases, so they make your work more easily findable. Since the abstract is the first thing any reader sees, it’s important that it clearly and accurately summarizes the contents of your paper.

An abstract for a thesis or dissertation is usually around 200–300 words. There’s often a strict word limit, so make sure to check your university’s requirements.

The abstract is the very last thing you write. You should only write it after your research is complete, so that you can accurately summarize the entirety of your thesis , dissertation or research paper .

Avoid citing sources in your abstract . There are two reasons for this:

• The abstract should focus on your original research, not on the work of others.
• The abstract should be self-contained and fully understandable without reference to other sources.

There are some circumstances where you might need to mention other sources in an abstract: for example, if your research responds directly to another study or focuses on the work of a single theorist. In general, though, don’t include citations unless absolutely necessary.

The abstract appears on its own page in the thesis or dissertation , after the title page and acknowledgements but before the table of contents .

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Honors291g-cdg’s blog, how to write a summary, synopsis, or abstract.

How to Write a Summary, Synopsis, or Abstract What is an abstract? An abstract is a brief overview of a document, book, or talk. The challenge in writing an abstract comes from providing a complete understanding of your source while also being concise. A well-written abstract gives your readers the opportunity to quickly and accurately identify the basic content and key themes of the source. You will see an abstract at the beginning of many scholarly journal articles, on the back of books, on DVDs of feature films, and other places where the reader needs a brief, but thorough snapshot of a source.

• Be concise. Abstracts are very brief, so state only what is essential. Use no more words than necessary to convey the information. A good abstract should not exceed 300 words. • Use active rather than passive verbs. See http://www.courses.umass.edu/envd394a/resources/action.html for a list of action verbs. • Do not use terms that are complicated or unfamiliar to you or your reader. • The title of the abstract is the same as the title of your source.

• Proofread your abstract several times.

Hint: A good place to find synopses is on www.amazon.com. Go to Books and enjoy!

Home » Education » Difference Between Abstract and Summary

Difference Between Abstract and Summary

Main difference – abstract vs summary.

Though the two terms abstract and summary are often used interchangeably, there is a distinct difference between abstract and summary. A summary is a condensed version of a longer work. An abstract is a brief summary that is found at the beginning of a research article, thesis, etc. This is the main difference between abstract and summary. An abstract is a type of summary.

What is an Abstract

An abstract is a short yet powerful statement or account that summarizes a larger work. It is a brief summary of a research paper, thesis, dissertation, etc. An abstract is typically found at the beginning of a document and it acts as an introduction and review of the whole document. It may contain information about the background, purpose, results, and contents of the work. An abstract typically contains four elements: research focus, research methods , results, main conclusions and recommendations.

An abstract can act as a stand-alone entity. Many organizations use abstracts as the basis for selecting research. In addition, most of the research articles available online are in the form of abstracts; the readers can decide whether they want to purchase the article by reading the abstract. Thus, it can be said that abstracts help the readers to decide whether they should invest time and money in reading the whole article.

What is a Summary

A summary is a brief statement or account containing the central points of a text. It can be defined as a condensed or abridged version of a text. Since it only contains the central and most important concepts, it is considerably shorter than the original text.

The term summary can refer to several things. A summary can be a synopsis of a book, article, film or play. Here, the outline of the plot can be termed as a summary. An executive summary, which is seen at the beginning of a business report , proposal and plan, is also a summary; it summarizes the entire content, highlighting the central points of the document. An abstract is also a similar summary that is used in research papers.

Abstract is a concise summary found at the beginning of a research article.

Summary is a brief statement or account of the main points of a longer work.

Interconnection

Abstract is a type of a summary.

Summary can be a synopsis, abstract or an executive summary.

Abstract should contain the research purpose, method, results, conclusion and recommendations.

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Differences between summary, abstract, overview, and synopsis

Are there subtle differences in meaning between the nouns summary , abstract , overview , and synopsis ?

Which would be the most appropriate term for a one-page "executive summary" of a research report?

From Wiktionary:

• summary : An abstract or a condensed presentation of the substance of a body of material.
• abstract : An abridgement or summary.
• overview : A brief summary, as of a book or a presentation.
• synopsis : A brief summary of the major points of a written work, either as prose or as a table; an abridgment or condensation of a work.
• differences

• Personally I would use 'synopsis' but any of them would work. –  WS2 Commented Feb 11, 2014 at 22:30
• Don't forget "précis"! Oh, and "thumbnail sketch," too. Précis certainly has some snob appeal, no? (I mean "Mais oui?") Don –  rhetorician Commented Feb 12, 2014 at 0:38
• 1 I like Professor David Barnhill's argument for precis: "A precis is a brief summary of a larger work. The term "abstract" has the same meaning and is much more common, but I prefer the term precis because of its relation to the word "precise," and because of the way the word is pronounced: "pray-see." A precis is a precise condensation of the basic thesis and major points of a paper; it tells the reader the gist of what has been said." uwosh.edu/facstaff/barnhill/490-docs/assignments/precis –  Mark D Worthen PsyD Commented Feb 23, 2018 at 0:24
• The difference is context. Context. –  Lambie Commented Dec 31, 2019 at 18:56

5 Answers 5

Summary is the most catch-all term of this group, and the one that shows up the most in general everyday English.

Abstract is most commonly used in the scientific context. It is typically a formal requirement for publication, as the initial section of a scientific paper. Often times if you find scientific papers online, it is just the abstract that is available.

Overview is similar in literal meaning to "summary". It has a slight informality to it.

Synopsis again could be exchanged directly for "summary" in most contexts. It has a slightly more formal feel, and shows up in the literature and the arts a bit more frequently than other contexts (e.g., "I just want to read a synopsis of the novel, not the whole thing" sounds a bit better than "summary"). A synopsis is often more detailed than a regular "summary".

Executive Summary shows up most often in a business context, or sometimes also in a political context (e.g., think-tank white papers).

Any of these would probably work in a research report, but it would also depend on the audience. Scientists would probably be most comfortable with "Abstract"; MBAs with "Executive Summary"; for a more general public audience where you want to seem accessible, "Overview". If you're not sure, I can't imagine going wrong with "Summary".

Note that I'm American, so this answer applies most directly to American English.

• 2 This one-page PDF from a community college writing center complements joseph_morris's excellent summary (above). jccc.edu/student-resources/tutors-accessibility/writing-center/… –  Mark D Worthen PsyD Commented Mar 7, 2018 at 2:53
• Also, there is somewhat called abrégé , which is placed right after the heading of each chapter. Abrégé is very (not longer then 1/2 of a page, i.e. it is shorter then typical abstract) and describes the chapter instead of document . (Feel free to correct me). –  john c. j. Commented Apr 7, 2018 at 22:26
• @johnc.j. As you can see from the Wiktionary article you link, abrégé is only a word in French. If it was an English word as well, it would have a separate listing under "English". –  joseph_morris Commented Apr 10, 2018 at 22:39
• It should also be noted that an abstract or an executive summary of a publication is typically set out separately from the rest of it, and is often labelled as such; the other terms can be used for something that is embedded in a larger body of text, without being clearly demarcated (e.g. the first chapter of a book may include a summary or an overview of the book's argument). –  jsw29 Commented Dec 30, 2019 at 17:20

synopsis suggests an outline or series of key points, sometimes implying restraint in keeping factual, objective, professional, or formal ("a synopsis of North American flora" or "a synopsis of the novel")

summary implies moving from the specific to the more general or the gist or take-away of something, and it is more likely to include the subjective ("summarized the movie as a bad coming-of-age drama")

overview implies a comprehensive, coherent whole or bird's-eye view ("gave an overview of the project")

abstract and precis both denote that the subject is a text

abstract is commonly used in technical and scientific contexts ("wrote an abstract for a scholarly journal article")

• Welcome to English SE! Could you edit to include citations for these definitions? This site generally prefers well-sourced answers, and unsourced ones may be removed. –  Rand al'Thor Commented Aug 7, 2017 at 8:06
• 1 +1 for reminding me of the phrase that I sought: bird's-eye view . Thanks. –  Graham Perrin Commented Oct 14, 2017 at 6:56

A little more detail:

The most appropriate term for a one page summary of a research report would normally be "Abstract", as it gives the abstract or high-level information without the details. The body may be labeled as "Detail". (They are essentially opposites, or complements. Abstract:Detail)

If the information is expected to summarize the points upon which a decision is to be made then "Executive Summary", meaning summary of the actionable parts, would be used.

See definitions of "Abstract" and "Executive" for the reasons this is so.

Although summary and synopsis are very close in meaning due to common usage, a summary is supposed to contain conclusions (sum, total) "In summary, therefore, I say to you .." while a synopsis is an overview.

I am an American English speaker.

• Also, there is somewhat called abrégé , which is placed right after the heading of each chapter. Abrégé is very (not longer then 1/2 of a page, i.e. it is shorter then typical abstract) and describes the chapter instead of document . (Feel free to correct me). –  john c. j. Commented Apr 7, 2018 at 22:25

None of the earlier answers to this question have cited any authority for the particular distinctions that they make. In case some readers may be interested in reference-work assessments of the relevant differences, I offer discussions from several such works. I should note at the outset that none of them include coverage of overview , although I have no idea why they don't.

James Fernald, Funk & Wagnalls Standard Handbook of Synonyms, Antonyms & Prepositions , revised edition (1947), includes coverage of abstract , summary , and synopsis (along with abbreviation , analysis , compend , compendium , digest , epitome , outline , and précis ) under the category name abridgment . Here is Fernald's coverage of the three terms of special interest:

An outline or synopsis is a kind of sketch closely following the plan [of a book]. An abstract or digest is an independent statement of what the book contains. ... A summary is the most condensed statement of results or conclusions.

This treatment of abstract , summary , and synopsis is identical to the treatment that appears in Fernald's English Synonyms and Antonyms , thirty-first edition (1914). In my view, while the descriptions of abstract and synopsis may still be accurate, the description of summary treats that word far more restrictively than most people do who use it today.

S. I. Hayakawa, Choose the Right Word: A Modern Guide to Synonyms (1968) groups abstract and synopsis (as well as abridgment , digest , outline , and précis ) under the category name summary . Here are the relevant portions of Hayakawa's coverage:

These words refer to a short description of the main points of a longer work or presentation. Summary is the most general of these words, referring to any attempt to condense into as few words as possible an extended train of thought: a day-to-day summary of the proceedings in the murder trial; concluding each chapter with a summary of its main arguments. The word implies a pithy paraphrase, with no attempt to catch the style of the original. Also, the word almost exclusively refers to something that follows after and is based on the extended presentation, or even concludes it—as suggested by the common phrase in speechmaking: in summary . Abstract and précis both refer to summaries written most often by someone other than the original author; hence they are seldom part of the original presentation, though they follow it and are based on it. Like summary , they stress brevity and the schematic representation of essential points with no attempt to preserve flavor. Abstract most specifically refers to a scholarly or legal citation that gives the gist of what may be a complex argument or study: a quarterly containing abstracts of doctoral dissertations in progress; an abstract of the proposed legislation. ... Outline and synopsis relate to précis in that they both retain the point-by-point ordering of the original; they are both most often a skeletal setting down of these points, but may be drawn up either by the author or someone else before, as well as after, the writing of the original. Within these possibilities, outline covers a wider range than synopsis . ... Synopsis usually refers to a plot summary of a piece of fiction. Ordinary prose sentences are most often used, rather than the numbered and lettered list suggested by outline . It may tell in capsule form events treated in a completed work or those planned for a projected work: submitting the first chapter of his novel and a synopsis of the unwritten remainder; writing synopses of novels submitted as candidates for film treatment. The word may also refer to a paragraph that retells previous action and introduces an installment of a serialized work of fiction.

Hayakawa's assessment of how people use summary is seems generally valid for today's usage, although in my experience an "executive summary" physically precedes a full report or article rather than following it.

Merriam-Webster's Dictionary of Synonyms (1968/1984) omits coverage of both overview and summary , but addresses abstract and synopsis as part of a larger group of words that also includes epitome , brief , and conspectus , under the category name abridgment :

abridgment , abstract , epitome , brief , synopsis , conspectus mean a condensation of a larger work or treatment, usually one already in circulation. ... Abstract implies condensation of a lengthy treatise or of a proposed lengthy treatment and stresses concentration of substance { abstracts of state papers} {an abstract of a lecture} ... Both abstract and epitome are used also in extended senses in reference to persons or things, the former stressing one or other (of the persons or things referred to) as a summary, the latter as a type representing a whole {a man who is the abstract of all faults that all men follow— Shak .} ... Synopsis and conspectus imply the giving of the salient points of a treatise or subject so that it may be quickly comprehended. Synopsis , however, often suggests an outline or coherent series of headings and conspectus a coherent account that gives a bird's-eye view {provide in advance a synopsis of the lectures}

As for overview , its meaning in modern English seems to be very close to that of summary , to judge from its brief entry in Merriam-Webster's Eleventh Collegiate Dictionary (2003):

overview n (1588) : a general survey : SUMMARY

Summary - Its sums up, like a conclusion, and is used at the end of the document. Many people, instead of reading the entire document that is large, refers to the summary.

Abstract - Mostly seen in journals that tells what it is all about, very briefly. Abstract is commonly seen in government orders too. Abstract comes at the start of the document.

Overview - It is a general view; not that analytical, and is often the beginning of an analysis.

Synopsis - Is a brief version of the manuscript which is sent to a publisher, on the basis of which the write-up/ manuscript is chosen.

Though all these refer to concise/abridged version of a manuscript, the purposes are different.

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• Online Guide to Writing

Patterns for Presenting Information

Summaries and Abstracts

When you summarize , you provide the main points of something: a book, an article, a movie, a play. Almost anything can be summarized, and if you work with source material at all while writing your college papers, you will inevitably summarize something. 

• Where to Summarize
• How to Summarize

Summaries are part of almost any paper. For example, a conclusion should include a summary of what has come before. Some papers, like article or book reviews, require summaries as a section of the paper. For other papers, you will be required to provide an “executive summary,” a prologue to a business document for executives who may only have time to read a summary of the document.

Present a balanced view of your material.

Give equal coverage to all parts of the material.

Use a neutral tone in your writing.

Keep the author’s material distortion-free. 

Summarize in your own words.

Take a class in the sciences or social sciences, and you will almost certainly read a scholarly article. You will notice that often the articles begin with something called an “ abstract .” This is a particular kind of summary. It helps readers determine whether to read the entire study. To the degree that an abstract differs from other summaries, it generally differs in emphasis. An abstract prioritizes the research question, thesis, and major findings of a work. When writing an abstract, your focus should be on the essential content of what you are summarizing.

Those who catalog information and create research reference materials also use abstracts. Most information-retrieval systems can scan the key words in an abstract and retrieve the source it is based on. 

Depending on the discipline in which you are writing, you may be asked to write an abstract for a research report, seminar paper, or a scholarly paper. Many graduate theses and dissertations require them.

Because abstracts help readers decide whether they want to read the original source, the content is quite compressed. Your abstract should contain only a few sentences, perhaps only three to five. You should include the key words that reveal the major idea of the original material to identify the field of study involved.

Key Takeaways

Summaries are condensed restatements of factual information.

Abstracts are condensed restatements of the main points and findings of an entire paper.

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Table of Contents: Online Guide to Writing

Chapter 1: College Writing

How Does College Writing Differ from Workplace Writing?

What Is College Writing?

Why So Much Emphasis on Writing?

Chapter 2: The Writing Process

Doing Exploratory Research

Getting from Notes to Your Draft

Introduction

Prewriting - Techniques to Get Started - Mining Your Intuition

Prewriting: Targeting Your Audience

Prewriting: Techniques to Get Started

Prewriting: Understanding Your Assignment

Rewriting: Being Your Own Critic

Rewriting: Creating a Revision Strategy

Rewriting: Getting Feedback

Rewriting: The Final Draft

Techniques to Get Started - Outlining

Techniques to Get Started - Using Systematic Techniques

Thesis Statement and Controlling Idea

Writing: Getting from Notes to Your Draft - Freewriting

Writing: Getting from Notes to Your Draft - Summarizing Your Ideas

Writing: Outlining What You Will Write

Chapter 3: Thinking Strategies

A Word About Style, Voice, and Tone

A Word About Style, Voice, and Tone: Style Through Vocabulary and Diction

Critical Strategies and Writing

Critical Strategies and Writing: Analysis

Critical Strategies and Writing: Evaluation

Critical Strategies and Writing: Persuasion

Critical Strategies and Writing: Synthesis

Developing a Paper Using Strategies

Kinds of Assignments You Will Write

Patterns for Presenting Information: Critiques

Patterns for Presenting Information: Discussing Raw Data

Patterns for Presenting Information: General-to-Specific Pattern

Patterns for Presenting Information: Problem-Cause-Solution Pattern

Patterns for Presenting Information: Specific-to-General Pattern

Patterns for Presenting Information: Summaries and Abstracts

Supporting with Research and Examples

Writing Essay Examinations

Writing Essay Examinations: Make Your Answer Relevant and Complete

Writing Essay Examinations: Organize Thinking Before Writing

Writing Essay Examinations: Read and Understand the Question

Chapter 4: The Research Process

Planning and Writing a Research Paper

Planning and Writing a Research Paper: Ask a Research Question

Planning and Writing a Research Paper: Cite Sources

Planning and Writing a Research Paper: Collect Evidence

Planning and Writing a Research Paper: Decide Your Point of View, or Role, for Your Research

Planning and Writing a Research Paper: Draw Conclusions

Planning and Writing a Research Paper: Find a Topic and Get an Overview

Planning and Writing a Research Paper: Manage Your Resources

Planning and Writing a Research Paper: Outline

Planning and Writing a Research Paper: Survey the Literature

Planning and Writing a Research Paper: Work Your Sources into Your Research Writing

Research Resources: Where Are Research Resources Found? - Human Resources

Research Resources: What Are Research Resources?

Research Resources: Where Are Research Resources Found?

Research Resources: Where Are Research Resources Found? - Electronic Resources

Research Resources: Where Are Research Resources Found? - Print Resources

Structuring the Research Paper: Formal Research Structure

Structuring the Research Paper: Informal Research Structure

The Nature of Research

The Research Assignment: How Should Research Sources Be Evaluated?

The Research Assignment: When Is Research Needed?

The Research Assignment: Why Perform Research?

Chapter 5: Academic Integrity

Academic Integrity

Giving Credit to Sources

Giving Credit to Sources: Copyright Laws

Giving Credit to Sources: Documentation

Giving Credit to Sources: Style Guides

Integrating Sources

Practicing Academic Integrity

Practicing Academic Integrity: Keeping Accurate Records

Practicing Academic Integrity: Managing Source Material

Practicing Academic Integrity: Managing Source Material - Paraphrasing Your Source

Practicing Academic Integrity: Managing Source Material - Quoting Your Source

Practicing Academic Integrity: Managing Source Material - Summarizing Your Sources

Types of Documentation

Types of Documentation: Bibliographies and Source Lists

Types of Documentation: Citing World Wide Web Sources

Types of Documentation: In-Text or Parenthetical Citations

Types of Documentation: In-Text or Parenthetical Citations - APA Style

Types of Documentation: In-Text or Parenthetical Citations - CSE/CBE Style

Types of Documentation: In-Text or Parenthetical Citations - Chicago Style

Types of Documentation: In-Text or Parenthetical Citations - MLA Style

Types of Documentation: Note Citations

Chapter 6: Using Library Resources

Finding Library Resources

Chapter 7: Assessing Your Writing

How Is Writing Graded?

How Is Writing Graded?: A General Assessment Tool

The Draft Stage

The Draft Stage: The First Draft

The Draft Stage: The Revision Process and the Final Draft

The Draft Stage: Using Feedback

The Research Stage

Using Assessment to Improve Your Writing

Chapter 8: Other Frequently Assigned Papers

Reviews and Reaction Papers: Article and Book Reviews

Reviews and Reaction Papers: Reaction Papers

Writing Arguments

Writing Arguments: Adapting the Argument Structure

Writing Arguments: Purposes of Argument

Writing Arguments: References to Consult for Writing Arguments

Writing Arguments: Steps to Writing an Argument - Anticipate Active Opposition

Writing Arguments: Steps to Writing an Argument - Determine Your Organization

Writing Arguments: Steps to Writing an Argument - Develop Your Argument

Writing Arguments: Steps to Writing an Argument - Introduce Your Argument

Writing Arguments: Steps to Writing an Argument - State Your Thesis or Proposition

Writing Arguments: Steps to Writing an Argument - Write Your Conclusion

Writing Arguments: Types of Argument

Appendix A: Books to Help Improve Your Writing

Dictionaries

General Style Manuals

Researching on the Internet

Special Style Manuals

Writing Handbooks

Appendix B: Collaborative Writing and Peer Reviewing

Collaborative Writing: Assignments to Accompany the Group Project

Collaborative Writing: Informal Progress Report

Collaborative Writing: Issues to Resolve

Collaborative Writing: Methodology

Collaborative Writing: Peer Evaluation

Collaborative Writing: Tasks of Collaborative Writing Group Members

Collaborative Writing: Writing Plan

General Introduction

Peer Reviewing

Appendix C: Developing an Improvement Plan

Working with Your Instructor’s Comments and Grades

Appendix D: Writing Plan and Project Schedule

Devising a Writing Project Plan and Schedule

Reviewing Your Plan with Others

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What Exactly is an Abstract, and How Do I Write One?

An abstract is a short summary of your completed research. It is intended to describe your work without going into great detail. Abstracts should be self-contained and concise, explaining your work as briefly and clearly as possible. Different disciplines call for slightly different approaches to abstracts, as will be illustrated by the examples below, so it would be wise to study some abstracts from your own field before you begin to write one.

General Considerations

Probably the most important function of an abstract is to help a reader decide if he or she is interested in reading your entire publication. For instance, imagine that you’re an undergraduate student sitting in the library late on a Friday night. You’re tired, bored, and sick of looking up articles about the history of celery. The last thing you want to do is reading an entire article only to discover it contributes nothing to your argument. A good abstract can solve this problem by indicating to the reader if the work is likely to be meaningful to his or her particular research project. Additionally, abstracts are used to help libraries catalogue publications based on the keywords that appear in them.

An effective abstract will contain several key features:

• Motivation/problem statement: Why is your research/argument important? What practical, scientific, theoretical or artistic gap is your project filling?
• Methods/procedure/approach: What did you actually do to get your results? (e.g. analyzed 3 novels, completed a series of 5 oil paintings, interviewed 17 students)
• Results/findings/product: As a result of completing the above procedure, what did you learn/invent/create?
• Conclusion/implications: What are the larger implications of your findings, especially for the problem/gap identified previously? Why is this research valuable?

In Practice

Let’s take a look at some sample abstracts, and see where these components show up. To give you an idea of how the author meets these “requirements” of abstract writing, the various features have been color-coded to correspond with the numbers listed above. The general format of an abstract is largely predictable, with some discipline-based differences. One type of abstract not discussed here is the “Descriptive Abstract,” which only summarizes and explains existing research, rather than informing the reader of a new perspective. As you can imagine, such an abstract would omit certain components of our four-colored model.

SAMPLE ABSTRACTS

Abstract #1: history / social science.

"Their War": The Perspective of the South Vietnamese Military in Their Own Words Author: Julie Pham

Despite the vast research by Americans on the Vietnam War, little is known about the perspective of South Vietnamese military, officially called the Republic of Vietnam Armed Forces (RVNAF). The overall image that emerges from the literature is negative: lazy, corrupt, unpatriotic, apathetic soldiers with poor fighting spirits. This study recovers some of the South Vietnamese military perspective for an American audience through qualititative interviews with 40 RVNAF veterans now living in San José, Sacramento, and Seattle, home to three of the top five largest Vietnamese American communities in the nation. An analysis of these interviews yields the veterans' own explanations that complicate and sometimes even challenge three widely held assumptions about the South Vietnamese military: 1) the RVNAF was rife with corruption at the top ranks, hurting the morale of the lower ranks; 2) racial relations between the South Vietnamese military and the Americans were tense and hostile; and 3) the RVNAF was apathetic in defending South Vietnam from communism. The stories add nuance to our understanding of who the South Vietnamese were in the Vietnam War. This study is part of a growing body of research on non-American perspectives of the war. In using a largely untapped source of Vietnamese history—oral histories with Vietnamese immigrants—this project will contribute to future research on similar topics.

That was a fairly basic abstract that allows us to examine its individual parts more thoroughly.

Motivation/problem statement: The author identifies that previous research has been done about the Vietnam War, but that it has failed to address the specific topic of South Vietnam’s military. This is good because it shows how the author’s research fits into the bigger picture. It isn’t a bad thing to be critical of other research, but be respectful from an academic standpoint (i.e. “Previous researchers are stupid and don’t know what they’re talking about” sounds kind of unprofessional).

Methods/procedure/approach: The author does a good job of explaining how she performed her research, without giving unnecessary detail. Noting that she conducted qualitative interviews with 40 subjects is significant, but she wisely does not explicitly state the kinds of questions asked during the interview, which would be excessive.

Results/findings/product: The results make good use of numbering to clearly indicate what was ascertained from the research—particularly useful, as people often just scan abstracts for the results of an experiment.

Conclusion/implications: Since this paper is historical in nature, its findings may be hard to extrapolate to modern-day phenomena, but the author identifies the importance of her work as part of a growing body of research, which merits further investigation. This strategy functions to encourage future research on the topic.

ABSTRACT #2: Natural Science

“A Lysimeter Study of Grass Cover and Water Table Depth Effects on Pesticide Residues in Drainage Water” Authors: A. Liaghat, S.O. Prasher

A study was undertaken to investigate the effect of soil and grass cover, when integrated with water table management (subsurface drainage and controlled drainage), in reducing herbicide residues in agricultural drainage water. Twelve PVC lysimeters, 1 m long and 450 mm diameter, were packed with a sandy soil and used to study the following four treatments: subsurface drainage, controlled drainage, grass (sod) cover, and bare soil. Contaminated water containing atrazine, metolachlor, and metribuzin residues was applied to the lysimeters and samples of drain effluent were collected. Significant reductions in pesticide concentrations were found in all treatments. In the first year, herbicide levels were reduced significantly (1% level), from an average of 250 mg/L to less than 10 mg/L . In the second year, polluted water of 50 mg/L, which is considered more realistic and reasonable in natural drainage waters, was applied to the lysimeters and herbicide residues in the drainage waters were reduced to less than 1 mg/L. The subsurface drainage lysimeters covered with grass proved to be the most effective treatment system.

Motivation/problem statement: Once again, we see that the problem—more like subject of study —is stated first in the abstract. This is normal for abstracts, in that you want to include the most important information first. The results may seem like the most important part of the abstract, but without mentioning the subject, the results won’t make much sense to readers. Notice that the abstract makes no references to other research, which is fine. It is not obligatory to cite other publications in an abstract, and in fact, doing so might distract your reader from YOUR experiment. Either way, it is likely that other sources will surface in your paper’s discussion/conclusion.

Methods/procedure/approach: Notice that the authors include pertinent numbers and figures in describing their methods. An extended description of the methods would probably include a long list of numerical values and conditions for each experimental trial, so it is important to include only the most important values in your abstract—ones that might make your study unique. Additionally, we see that a methodological description appears in two different parts of the abstract. This is fine. It may work better to explain your experiment by more closely connecting each method to its result. One last point: the author doesn’t take time to define—or give any background information about—“atrazine,” “metalachlor,” “lysimeter,” or “metribuzin.” This may be because other ecologists know what these are, but even if that’s not the case, you shouldn’t take time to define terms in your abstract.

Results/findings/product: Similar to the methods component of the abstract, you want to condense your findings to include only the major result of the experiment. Again, this study focused on two major trials, so both trials and both major results are listed. A particularly important word to consider when sharing results in an abstract is “significant.” In statistics, “significant” means roughly that your results were not due to chance. In your paper, your results may be hundreds of words long, and involve dozens of tables and graphs, but ultimately, your reader only wants to know: “What was the main result, and was that result significant?” So, try to answer both these questions in the abstract.

Conclusion/implications: This abstract’s conclusion sounds more like a result: “…lysimeters covered with grass were found to be the most effective treatment system.” This may seem incomplete, since it does not explain how this system could/should/would be applied to other situations, but that’s okay. There is plenty of space for addressing those issues in the body of the paper.

ABSTRACT #3: Philosophy / Literature

[Note: Many papers don’t precisely follow the previous format, since they do not involve an experiment and its methods. Nonetheless, they typically rely on a similar structure.]

“Participatory Legitimation: A Reply to Arash Abizadeh” Author: Eric Schmidt, Louisiana State University, 2011

Arash Abizadeh’s argument against unilateral border control relies on his unbounded demos thesis, which is supported negatively by arguing that the ‘bounded demos thesis’ is incoherent. The incoherency arises for two reasons: (1) Democratic principles cannot be brought to bear on matters (border control) logically prior to the constitution of a group, and (2), the civic definition of citizens and non-citizens creates an ‘externality problem’ because the act of definition is an exercise of coercive power over all persons. The bounded demos thesis is rejected because the “will of the people” fails to legitimate democratic political order because there can be no pre-political political will of the people. However, I argue that “the will of the people” can be made manifest under a robust understanding of participatory legitimation, which exists concurrently with the political state, and thus defines both its borders and citizens as bounded , rescuing the bounded demos thesis and compromising the rest of Abizadeh’s article.

This paper may not make any sense to someone not studying philosophy, or not having read the text being critiqued. However, we can still see where the author separates the different components of the abstract, even if we don’t understand the terminology used.

Motivation/problem statement: The problem is not really a problem, but rather another person’s belief on a subject matter. For that reason, the author takes time to carefully explain the exact theory that he will be arguing against.

Methods/procedure/approach: [Note that there is no traditional “Methods” component of this abstract.] Reviews like this are purely critical and don’t necessarily involve performing experiments as in the other abstracts we have seen. Still, a paper like this may incorporate ideas from other sources, much like our traditional definition of experimental research.

Results/findings/product: In a paper like this, the “findings” tend to resemble what you have concluded about something, which will largely be based on your own opinion, supported by various examples. For that reason, the finding of this paper is: “The ‘will of the people,’ actually corresponds to a ‘bounded demos thesis.’” Even though we aren’t sure what the terms mean, we can plainly see that the finding (argument) is in support of “bounded,” rather than “unbounded.”

Conclusion/implications: If our finding is that “bounded” is correct, then what should we conclude? [In this case, the conclusion is simply that the initial author, A.A., is wrong.] Some critical papers attempt to broaden the conclusion to show something outside the scope of the paper. For example, if A.A. believes his “unbounded demos thesis” to be correct (when he is actually mistaken), what does this say about him? About his philosophy? About society as a whole? Maybe people who agree with him are more likely to vote Democrat, more likely to approve of certain immigration policies, more likely to own Labrador retrievers as pets, etc.

Applying These Skills

Now that you know the general layout of an abstract, here are some tips to keep in mind as you write your own:

1. The abstract stands alone

An abstract shouldn’t be considered “part” of a paper—it should be able to stand independently and still tell the reader something significant.

2. Keep it short

A general rule of abstract length is 200-300 words, or about 1/10th of the entire paper.

3. Don’t add new information

If something doesn’t appear in your actual paper, then don’t put it in the abstract.

4. Be consistent with voice, tone, and style

Try to write the abstract in the same style as your paper (i.e. If you’re not using contractions in your paper, the do not use them in your abstract).

5. Be concise

Try to shorten your sentences as often as possible. If you can say something clearly in five words rather than ten, then do it.

6. Break up its components

If allowed, subdivide the components of your abstract with bolded headings for “Background,” “Methods,” etc.

7. The abstract should be part of your writing process

Consider writing your abstract after you finish your entire paper.

There’s nothing wrong with copying and pasting important sentences and phrases from your paper … provided that they’re your own words.

Write multiple drafts, and keep revising. An abstract is very important to your publication (or assignment) and should be treated as such.

"Abstracts." The Writing Center. The University of North Carolina, n.d. Web. 1 Jun 2011. http://www.unc.edu/depts/wcweb/handouts/abstracts.html

"Abstracts." The Writing Center. Rensselaer Polytechnic Institute, n.d. Web. 1 Jun 2011. http://www.rpi.edu/web/writingcenter/abstracts.html

Last updated August 2013

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Frequently asked questions

What’s the difference between an abstract and a summary.

An abstract concisely explains all the key points of an academic text such as a thesis , dissertation or journal article. It should summarise the whole text, not just introduce it.

An abstract is a type of summary , but summaries are also written elsewhere in academic writing . For example, you might summarise a source in a paper , in a literature review , or as a standalone assignment.

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Educational resources and simple solutions for your research journey

How to Write a Lay Summary: 10 Tips for Researchers

Once you know what a lay summary is, the next question you’ll probably be asking yourself is ‘how to write a lay summary?’ But why is this important for researchers? For one, there has been a surge in research output. The past decade has seen a 4% annual increase in peer-reviewed science and engineering (S&E) journal articles and conference papers being published. 1 However, it’s not just the increasing number of published articles but the visibility your work receives that indicates a researcher’s productivity and success. While researchers often come up with ground-breaking and crucial findings, it can be challenging for non-academics and even specialists from other disciplines to understand its importance. Communicating research findings to a broader audience is a crucial aspect of any scholarly work. So in this article, we will explore the importance of writing a lay summary, explaining how to write a lay summary to ensure your research reaches and resonates with a wider audience.

Table of Contents

What is a lay summary in research?

Lay summaries are condensed descriptions of research findings that are written in a simple way so that wider audience can understand the work presented with ease. Writing a lay summary also aids in bridging the gap between often complex research work and non-specialist readers, providing them with a clear overview of the research’s purpose, key findings, and real-world implications. By making the published study more widely available, researchers can foster inclusivity, promote wider engagement, and spark new research, and influence public policy. Writing a lay summary in a simple, compelling manner goes a long way in not only ensuring visibility, it also makes it more comprehensible and usable for journalists, policymakers, and people around the world.

4 Reasons you need to write an effective lay summary

• Create greater visibility: An impactful lay summary is a great way of describing and communicating details of the research done to the general public and can help those who don’t have an academic background to better understand your work.
• Enhance transparency: A well-crafted lay summary can boost transparency, adding to the reliability and credibility of your research. A lay summary that describes and communicates your research findings in a clear, simple way leaves little room for misrepresentation.
• Improve engagement: A succinct lay summary makes research findings easier to understand and highlights its significance. This means that audiences can engage more actively with your work, leading to an increase in the number of citations.
• Widen research impact: Writing a lay summary that is engaging and compelling helps researchers effectively convey their research findings, emphasize their work’s applicability and potential, and drive real-world impact.

How to write a lay summary of scientific papers

A lay summary of a scientific paper doesn’t have to be challenging to write. Here are some simple steps to keep in mind when writing a lay summary.

1. Identify your audience

Before you start crafting your lay summary, consider who your target audience is and tailor your language accordingly. This will make your lay summary more engaging and relevant to your readers, whether they’re policymakers, patients, or the general public.

2. Keep it simple, yet informative

Simplicity is the key to an effective lay summary, so avoid jargon and technical terms that might confuse your readers. Think of it as telling a story rather than presenting scientific data and focus on conveying the core message of your research in straightforward manner.

3. Highlight the importance

Describe the real-world impact of your findings and how they contribute to solving relevant issues or advancing knowledge in your field. Clearly articulating the significance of your work can keep your readers interested and invested in your research.

4. Follow a logical structure

A well-structured lay summary guides the reader through your research logically, step by step. When writing a lay summary, cover the problem you aimed to address, your methodology and key findings, and the implications and potential applications of your research.

5. Provide relevant context

Avoid assuming prior knowledge from your audience, provide enough context and background information to help readers understand your research without overwhelming them with technical details.

6. Use engaging examples

Analogies or real-life scenarios can help your audience grasp complex concepts and appreciate the relevance of your research. So integrate relatable examples when writing a lay summary.

7. Emphasize the benefits

Highlight the benefits of your research, how it can improve lives or contribute to societal advancements, and the practical implications of your work to resonate with readers.

8. Add the final touches

Employ formatting styles like subheads and bullet points and add visual elements like illustrations, tables, or graphs, to easily present data. Write a catchy headline or introduction and use a conversational tone when writing the lay summary.

9. Seek peer feedback

Get colleagues or friends outside your field to review your lay summary. Their feedback will help you gauge whether your summary successfully conveys the essence of your research to a broader audience.

10. Proofread and edit

As the last step, proofread and edit your work to polish language, grammar, punctuation, and sentence structure. Clear, error-free writing lends credibility to your research, ensuring it’s taken seriously and leaves a lasting impression on your readers.

Lay Summaries vs. Abstracts

It is common for to get confused between research paper abstracts and lay summaries. While both are used to convey research findings, they have vastly different purposes and audiences.

Abstracts provide a synopsis of a research project that is written for an audience of scholars and experts interested in a particular field of study. An abstract usually includes complex concepts and technical terms when trying to explain the relevance of the research topic. Researchers use an abstract to outline and highlight their objectives, approach, and finding. Abstracts provide a summary of the research paper so that readers may quickly grasp its ideas and decide whether it is pertinent to their areas of interest. An abstract requires usually is more detailed and longer than a lay summary.

Lay summaries on the other hand offer non-technical explanations of a research project. It is typically written for a wider audience, including non-academics and experts from other fields. A lay summary’s main objective is to make the study findings accessible to those who are not subject-matter experts by using analogies to simplify concepts. They highlight the practical relevance of the research in a succinct, impactful way.

Though both lay summaries and abstracts are different, if written in a compelling way, they can be powerful tools to engage readers and help you garner greater visibility for your work.

References:

1.       India is world’s third largest producer of scientific articles, following China and US: Report. India Today, Jan 2, 2020. Available online at https://www.indiatoday.in/education-today/latest-studies/story/india-is-world-s-third-largest-producer-of-scientific-articles-following-china-and-us-report-1633351-2020-01-02

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What’s the difference between an Abstract and a Summary?

By   Harry Heijligers

January 14, 2021

Abstract vs Summary... that's the question.

You have spend hours, weeks even researching and writing that article, report, academic, paper...

And now, just before you want to publish it...

You ask yourself: Should I write an abstract or should I write a summary?

Abstracts and summaries both have a lot of power when it comes to promoting your article, report, research paper, or even book.

Often the terms abstract and summary are confused with each other.

There is an essential difference!

And it's important to understand what the difference is between an abstract and a summary.

After all...

After putting in all that hard and long work to complete your article or report, it would a shame when no one will ever read it!

To answer the question of what the difference is between an abstract and a summary, I first want to define both the terms abstract and summary.

Let’s start with the term summary...

What is a summary and why should you use it?

Summaries are a great way to view the main ideas from a long article.

Summaries are great for readers when they...

• don’t have time to read the entire article.
• want to decide whether or not reading the article is worth their time.
• want to get an overview of the article quickly. It's a great starting point for reading the article.
• want to remember what the article was about in case they read it a while ago.

A good summary helps to start the thinking process in the reader's mind. One of the objectives of a summary is to make the reader curious about the article itself. To make the reader eager to read further.

A summary is not a substitute for an article. Rather, it’s a tool to help you read only the parts of an article that are important to you and to get answers quickly.

Creating a good summary takes time.

• You must read the original article carefully, sometimes more than once, and select the most important points.
• Then, in writing your summary, try to match the order of the original article, and include only the important points.
• Finally, edit your summary to improve its readability, clarity, and conciseness.

A summary doesn’t necessarily have to follow the order and sequence of the original article. A summary can have “a life on its own”. It’s the ad copy for your article to persuade the reader to read your article.

Executive summaries are often used to give the highlights of a report for a specific group of readers.

The same report can have an executive summary tied to their specific interest while another group of readers get's an executive summary highlighting other topics. Almost telling a whole "other" story.

Executive summaries are especially often used in large organizations and corporations where for example the local government needs to be told another story than the local works council.

In this respect, a summary differs from an abstract, because it can be more open-ended than an abstract and...

What is an abstract and why should you use it?

An abstract is a short section of text that reflects the contents of a large article or report. Abstracts are mostly written specifically for research papers.

The objective of an abstract is to give an overview of the paper’s content. It should persuade the reader to read the entire paper.

Most abstracts are structured abstracts because of the specific guidelines they have to follow.

Especially for academic reports , an abstract has specific guidelines and rules to follow. One of those rules is that the whole research paper should be reflected in the abstract in the exact sequential order as the paper itself.

Another type of abstract is the graphical abstract. A graphical abstract is a visual representation of what is told in the report. Visuals can be very powerful to convey a lot of information in just one picture.

As you have learned by now, a detailed description should be avoided in an abstract or summary. But where a summary can be focused on just one or two highlights from the original report, an abstract should be an accurate description of the article.

The difference between an abstract vs summary is that an abstract is like a 100% reflection of the contents of the article whereas a summary can highlight certain important aspects of the article.

The method you have used to do your research or to come to your conclusions should also be reflected in an abstract, more so than in a summary.

A summary helps the reader to focus on the important aspects of your article.

Abstract vs Summary: final verdict

When you are writing an article an important question to ask yourself, is should I write an abstract vs summary?

To help you ask this question, answer these questions first:

• What is the purpose of my abstract vs summary?
• Do I need to follow specific guidance from stakeholders or for my readers?
• Or can is the most important object of this abstract/summary to persuade my readers?

Depending on your answers to these questions you need to decide:

• Do I need to write an abstract?
• Do I need to write a summary?
• Do I need to write multiple summaries tied to multiple audiences?

Over to you:

Let me know in the comments below what your personal preference is with regards to abstract vs summary...

as a reader...

and as an author.

• Do you as a reader prefer to read an abstract more than a summary?
• Do you as an author prefer to write and develop an abstract more than you would prefer a summary?

Harry Heijligers

About the author

Harry Heijligers has more than 25 years of experience as a Project Manager and more than 17 years of experience as an NLP Trainer. He has a Dutch blog about NLP here: HarryHeijligers.com . If you'd like to know about the Smart Leadership Hut, please check this: Smart Leadership Hut .

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Abstract vs. Executive Summary

What's the difference.

Abstract and executive summary are both concise summaries of a longer document or report, but they serve different purposes. An abstract is typically found at the beginning of an academic paper or research article and provides a brief overview of the study's objectives, methods, results, and conclusions. It is meant to help readers quickly understand the main points of the research without having to read the entire document. On the other hand, an executive summary is commonly found in business reports or proposals and aims to provide a condensed version of the key findings, recommendations, and action plans. It is designed to give busy executives or decision-makers a snapshot of the report's content so they can make informed decisions without delving into the details.

Further Detail

Introduction.

When it comes to summarizing complex information, two commonly used tools are the abstract and executive summary. Both serve the purpose of providing a concise overview of a longer document, such as a research paper, report, or business plan. While they share similarities in terms of their purpose, there are distinct differences in their attributes and usage. In this article, we will explore the characteristics of abstracts and executive summaries, highlighting their unique features and discussing their respective benefits.

Definition and Purpose

An abstract is a brief summary of a document that provides an overview of the main points, arguments, and conclusions. It is typically found at the beginning of an academic paper or article and aims to give readers a quick understanding of the content without having to read the entire document. On the other hand, an executive summary is a condensed version of a longer report or business plan, often used in the corporate world. It serves as a standalone document that provides key information and recommendations to decision-makers, allowing them to grasp the main findings and make informed decisions.

Length and Content

One of the primary differences between abstracts and executive summaries lies in their length and content. Abstracts are usually shorter, ranging from 100 to 300 words, depending on the document's length. They focus on summarizing the main points, methodology, and results of the document, providing a glimpse into the overall structure and findings. In contrast, executive summaries are longer and more detailed, typically ranging from one to several pages. They include additional sections such as an introduction, background information, analysis, and recommendations, offering a comprehensive overview of the entire document.

Audience and Context

Another important aspect to consider when comparing abstracts and executive summaries is their intended audience and context of use. Abstracts are primarily targeted at researchers, scholars, and academics who are interested in the specific topic or field. They are often published alongside the full document in academic journals or databases, allowing readers to quickly assess the relevance and significance of the research. On the other hand, executive summaries are designed for a broader audience, including executives, managers, investors, or stakeholders who need to make informed decisions based on the summarized information. They are commonly used in business settings, board meetings, or when seeking funding or approval for a project.

Structure and Language

Abstracts and executive summaries also differ in terms of their structure and language. Abstracts typically follow a standardized format, including sections such as background, objectives, methods, results, and conclusion. They use concise and objective language, avoiding personal opinions or subjective statements. Executive summaries, on the other hand, have a more flexible structure depending on the document they summarize. They often include an introduction, problem statement, analysis of findings, and recommendations. The language used in executive summaries can be more persuasive and tailored to the target audience, incorporating strategic language and emphasizing key points to influence decision-making.

Usage and Benefits

Both abstracts and executive summaries offer unique benefits and serve different purposes in various contexts. Abstracts are essential for researchers and academics as they allow them to quickly assess the relevance and quality of a document before investing time in reading the full text. They help researchers identify relevant sources for their own work and provide a concise summary of the research landscape. On the other hand, executive summaries are valuable tools for decision-makers in the business world. They save time by providing a comprehensive overview of a report or business plan, enabling executives to make informed decisions without having to read the entire document. Executive summaries also facilitate effective communication and collaboration among team members, ensuring everyone is on the same page and aligned with the document's objectives.

In conclusion, abstracts and executive summaries are both powerful tools for summarizing complex information and providing a concise overview of longer documents. While abstracts are commonly used in academic settings to help researchers assess the relevance and quality of a document, executive summaries are widely used in the corporate world to facilitate decision-making and effective communication. Understanding the attributes and differences between abstracts and executive summaries is crucial for utilizing them effectively in their respective contexts. By leveraging these tools, individuals and organizations can save time, make informed decisions, and enhance collaboration and understanding among stakeholders.

Comparisons may contain inaccurate information about people, places, or facts. Please report any issues.

How to Write an Abstract?

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An abstract is a crisp, short, powerful, and self-contained summary of a research manuscript used to help the reader swiftly determine the paper’s purpose. Although the abstract is the first paragraph of the manuscript it should be written last when all the other sections have been addressed.

Research is formalized curiosity. It is poking and prying with a purpose. — Zora Neale Hurston, American Author, Anthropologist and Filmmaker (1891–1960)

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Writing the Abstract

Abstract and Keywords

Additional Commentaries

1 what is an abstract.

An abstract is usually a standalone document that informs the reader about the details of the manuscript to follow. It is like a trailer to a movie, if the trailer is good, it stimulates the audience to watch the movie. The abstract should be written from scratch and not ‘cut –and-pasted’ [ 1 ].

2 What is the History of the Abstract?

An abstract, in the form of a single paragraph, was first published in the Canadian Medical Association Journal in 1960 with the idea that the readers may not have enough time to go through the whole paper, and the first abstract with a defined structure was published in 1991 [ 2 ]. The idea sold and now most original articles and reviews are required to have a structured abstract. The abstract attracts the reader to read the full manuscript [ 3 ].

3 What are the Qualities of a Good Abstract?

The quality of information in an abstract can be summarized by four ‘C’s. It should be:

C: Condensed

C: Critical

4 What are the Types of Abstract?

Before writing the abstract, you need to check with the journal website about which type of abstract it requires, with its length and style in the ‘Instructions to Authors’ section.

The abstract types can be divided into:

Descriptive: Usually written for psychology, social science, and humanities papers. It is about 50–100 words long. No conclusions can be drawn from this abstract as it describes the major points in the paper.

Informative: The majority of abstracts for science-related manuscripts are informative and are surrogates for the research done. They are single paragraphs that provide the reader an overview of the research paper and are about 100–150 words in length. Conclusions can be drawn from the abstracts and in the recommendations written in the last line.

Critical: This type of abstract is lengthy and about 400–500 words. In this, the authors’ own research is discussed for reliability, judgement, and validation. A comparison is also made with similar studies done earlier.

Highlighting: This is rarely used in scientific writing. The style of the abstract is to attract more readers. It is not a balanced or complete overview of the article with which it is published.

Structured: A structured abstract contains information under subheadings like background, aims, material and methods, results, conclusion, and recommendations (Fig. 15.1 ). Most leading journals now carry these.

Example of a structured abstract (with permission editor CMRP)

5 What is the Purpose of an Abstract?

An abstract is written to educate the reader about the study that follows and provide an overview of the science behind it. If written well it also attracts more readers to the article. It also helps the article getting indexed. The fate of a paper both before and after publication often depends upon its abstract. Most readers decide if a paper is worth reading on the basis of the abstract. Additionally, the selection of papers in systematic reviews is often dependent upon the abstract.

6 What are the Steps of Writing an Abstract?

An abstract should be written last after all the other sections of an article have been addressed. A poor abstract may turn off the reader and they may cause indexing errors as well. The abstract should state the purpose of the study, the methodology used, and summarize the results and important conclusions. It is usually written in the IMRAD format and is called a structured abstract [ 4 , 5 ].

I: The introduction in the opening line should state the problem you are addressing.

M: Methodology—what method was chosen to finish the experiment?

R: Results—state the important findings of your study.

D: Discussion—discuss why your study is important.

Mention the following information:

Important results with the statistical information ( p values, confidence intervals, standard/mean deviation).

Arrange all information in a chronological order.

Do not repeat any information.

The last line should state the recommendations from your study.

The abstract should be written in the past tense.

7 What are the Things to Be Avoided While Writing an Abstract?

Cut and paste information from the main text

Hold back important information

Use abbreviations

Tables or Figures

Generalized statements

Arguments about the study

8 What are Key Words?

These are important words that are repeated throughout the manuscript and which help in the indexing of a paper. Depending upon the journal 3–10 key words may be required which are indexed with the help of MESH (Medical Subject Heading).

9 How is an Abstract Written for a Conference Different from a Journal Paper?

The basic concept for writing abstracts is the same. However, in a conference abstract occasionally a table or figure is allowed. A word limit is important in both of them. Many of the abstracts which are presented in conferences are never published in fact one study found that only 27% of the abstracts presented in conferences were published in the next five years [ 6 ].

Table 15.1 gives a template for writing an abstract.

10 What are the Important Recommendations of the International Committees of Medical Journal of Editors?

The recommendations are [ 7 ]:

An abstract is required for original articles, metanalysis, and systematic reviews.

A structured abstract is preferred.

The abstract should mention the purpose of the scientific study, how the procedure was carried out, the analysis used, and principal conclusion.

Clinical trials should be reported according to the CONSORT guidelines.

The trials should also mention the funding and the trial number.

The abstract should be accurate as many readers have access only to the abstract.

11 Conclusions

An Abstract should be written last after all the other sections of the manuscript have been completed and with due care and attention to the details.

It should be structured and written in the IMRAD format.

For many readers, the abstract attracts them to go through the complete content of the article.

The abstract is usually followed by key words that help to index the paper.

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Samiran Nundy

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Institute for Global Health and Development, The Aga Khan University, South Central Asia, East Africa and United Kingdom, Karachi, Pakistan

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Nundy, S., Kakar, A., Bhutta, Z.A. (2022). How to Write an Abstract?. In: How to Practice Academic Medicine and Publish from Developing Countries?. Springer, Singapore. https://doi.org/10.1007/978-981-16-5248-6_15

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An executive summary is a thorough overview of a research report or other type of document that synthesizes key points for its readers, saving them time and preparing them to understand the study's overall content. It is a separate, stand-alone document of sufficient detail and clarity to ensure that the reader can completely understand the contents of the main research study. An executive summary can be anywhere from 1-10 pages long depending on the length of the report, or it can be the summary of more than one document [e.g., papers submitted for a group project].

Bailey, Edward, P. The Plain English Approach to Business Writing . (New York: Oxford University Press, 1997), p. 73-80 Todorovic, Zelimir William and Marietta Wolczacka Frye. “Writing Effective Executive Summaries: An Interdisciplinary Examination.” In United States Association for Small Business and Entrepreneurship. Conference Proceedings . (Decatur, IL: United States Association for Small Business and Entrepreneurship, 2009): pp. 662-691.

Importance of a Good Executive Summary

Although an executive summary is similar to an abstract in that they both summarize the contents of a research study, there are several key differences. With research abstracts, the author's recommendations are rarely included, or if they are, they are implicit rather than explicit. Recommendations are generally not stated in academic abstracts because scholars operate in a discursive environment, where debates, discussions, and dialogs are meant to precede the implementation of any new research findings. The conceptual nature of much academic writing also means that recommendations arising from the findings are distributed widely and not easily or usefully encapsulated. Executive summaries are used mainly when a research study has been developed for an organizational partner, funding entity, or other external group that participated in the research . In such cases, the research report and executive summary are often written for policy makers outside of academe, while abstracts are written for the academic community. Professors, therefore, assign the writing of executive summaries so students can practice synthesizing and writing about the contents of comprehensive research studies for external stakeholder groups.

When preparing to write, keep in mind that:

• An executive summary is not an abstract.
• An executive summary is not an introduction.
• An executive summary is not a preface.
• An executive summary is not a random collection of highlights.

Christensen, Jay. Executive Summaries Complete The Report. California State University Northridge; Clayton, John. "Writing an Executive Summary that Means Business." Harvard Management Communication Letter (July 2003): 2-4; Keller, Chuck. "Stay Healthy with a Winning Executive Summary." Technical Communication 41 (1994): 511-517; Murphy, Herta A., Herbert W. Hildebrandt, and Jane P. Thomas. Effective Business Communications . New York: McGraw-Hill, 1997; Vassallo, Philip. "Executive Summaries: Where Less Really is More." ETC.: A Review of General Semantics 60 (Spring 2003): 83-90 .

Structure and Writing Style

Writing an Executive Summary

Read the Entire Document This may go without saying, but it is critically important that you read the entire research study thoroughly from start to finish before you begin to write the executive summary. Take notes as you go along, highlighting important statements of fact, key findings, and recommended courses of action. This will better prepare you for how to organize and summarize the study. Remember this is not a brief abstract of 300 words or less but, essentially, a mini-paper of your paper, with a focus on recommendations.

Isolate the Major Points Within the Original Document Choose which parts of the document are the most important to those who will read it. These points must be included within the executive summary in order to provide a thorough and complete explanation of what the document is trying to convey.

Separate the Main Sections Closely examine each section of the original document and discern the main differences in each. After you have a firm understanding about what each section offers in respect to the other sections, write a few sentences for each section describing the main ideas. Although the format may vary, the main sections of an executive summary likely will include the following:

• An opening statement, with brief background information,
• The purpose of research study,
• Method of data gathering and analysis,
• Overview of findings, and,
• A description of each recommendation, accompanied by a justification. Note that the recommendations are sometimes quoted verbatim from the research study.

Combine the Information Use the information gathered to combine them into an executive summary that is no longer than 10% of the original document. Be concise! The purpose is to provide a brief explanation of the entire document with a focus on the recommendations that have emerged from your research. How you word this will likely differ depending on your audience and what they care about most. If necessary, selectively incorporate bullet points for emphasis and brevity. Re-read your Executive Summary After you've completed your executive summary, let it sit for a while before coming back to re-read it. Check to make sure that the summary will make sense as a separate document from the full research study. By taking some time before re-reading it, you allow yourself to see the summary with fresh, unbiased eyes.

Common Mistakes to Avoid

Length of the Executive Summary As a general rule, the correct length of an executive summary is that it meets the criteria of no more pages than 10% of the number of pages in the original document, with an upper limit of no more than ten pages [i.e., ten pages for a 100 page document]. This requirement keeps the document short enough to be read by your audience, but long enough to allow it to be a complete, stand-alone synopsis. Cutting and Pasting With the exception of specific recommendations made in the study, do not simply cut and paste whole sections of the original document into the executive summary. You should paraphrase information from the longer document. Avoid taking up space with excessive subtitles and lists, unless they are absolutely necessary for the reader to have a complete understanding of the original document. Consider the Audience Although unlikely to be required by your professor, there is the possibility that more than one executive summary will have to be written for a given document [e.g., one for policy-makers, one for private industry, one for philanthropists]. This may only necessitate the rewriting of the introduction and conclusion, but it could require rewriting the entire summary in order to fit the needs of the reader. If necessary, be sure to consider the types of audiences who may benefit from your study and make adjustments accordingly. Clarity in Writing One of the biggest mistakes you can make is related to the clarity of your executive summary. Always note that your audience [or audiences] are likely seeing your research study for the first time. The best way to avoid a disorganized or cluttered executive summary is to write it after the study is completed. Always follow the same strategies for proofreading that you would for any research paper. Use Strong and Positive Language Don’t weaken your executive summary with passive, imprecise language. The executive summary is a stand-alone document intended to convince the reader to make a decision concerning whether to implement the recommendations you make. Once convinced, it is assumed that the full document will provide the details needed to implement the recommendations. Although you should resist the temptation to pad your summary with pleas or biased statements, do pay particular attention to ensuring that a sense of urgency is created in the implications, recommendations, and conclusions presented in the executive summary. Be sure to target readers who are likely to implement the recommendations.

Bailey, Edward, P. The Plain English Approach to Business Writing . (New York: Oxford University Press, 1997), p. 73-80; Christensen, Jay. Executive Summaries Complete The Report. California State University Northridge; Executive Summaries. Writing@CSU. Colorado State University; Clayton, John. "Writing an Executive Summary That Means Business." Harvard Management Communication Letter , 2003; Executive Summary. University Writing Center. Texas A&M University;  Green, Duncan. Writing an Executive Summary.   Oxfam’s Research Guidelines series ; Guidelines for Writing an Executive Summary. Astia.org; Markowitz, Eric. How to Write an Executive Summary. Inc. Magazine, September, 15, 2010; Kawaski, Guy. The Art of the Executive Summary. "How to Change the World" blog; Keller, Chuck. "Stay Healthy with a Winning Executive Summary." Technical Communication 41 (1994): 511-517; The Report Abstract and Executive Summary. The Writing Lab and The OWL. Purdue University; Writing Executive Summaries. Effective Writing Center. University of Maryland; Kolin, Philip. Successful Writing at Work . 10th edition. (Boston, MA: Cengage Learning, 2013), p. 435-437; Moral, Mary. "Writing Recommendations and Executive Summaries." Keeping Good Companies 64 (June 2012): 274-278; Todorovic, Zelimir William and Marietta Wolczacka Frye. “Writing Effective Executive Summaries: An Interdisciplinary Examination.” In United States Association for Small Business and Entrepreneurship. Conference Proceedings . (Decatur, IL: United States Association for Small Business and Entrepreneurship, 2009): pp. 662-691.

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In a nutshell: how to write a lay summary

November 26, 2018 | 5 min read

By Christopher Tancock

Why “translating” your research for a general audience can bring many benefits – and how to do so

With thanks to Kristina Killgrove

Elsevier Authors' Update is pleased to present this article in support of  PHD2Published Academic Writing Month. opens in new tab/window

You must be rather pleased with that newly-published article. After many long months, your hard work has paid off and that paper has now taken its place in the library of academic literature. Unfortunately, so have another 2.5 million articles just this year. How do you stand out amongst that enormous crowd and get attention? One way of doing this is to make your article as accessible as possible and a good way of achieving that aim is to prepare a lay summary.

What is a lay summary?

Though your colleagues and peers are probably able to get to grips with your article, the chances are that its content will be unintelligible to the average man or woman in the street. What’s more, researchers are increasingly tasked by their institutions and funders to outline the impact of their research for the general public and beyond their specific area of interest. If you can transform your article into something that the wider public can understand, you’ve got yourself another readership  - and one who is more likely to share what it is that you’ve discovered/hypothesized/confirmed further. The key to doing this is in producing a lay summary.

A lay summary, or impact statement, is a very efficient way of conveying the essence of your article briefly and clearly. Fundamentally, what you’re aiming to produce is a short paragraph outlining the article content, aimed at non-specialists in the field and written in a way that they can easily understand. This element differentiates it from the abstract, which is designed with your subject peers in mind. The structure of a lay summary should answer the main questions of “who/what/where/when/how many/why?” (in essence, you’re trying to justify why someone should spend time in reading what you’ve produced). Answering these questions in a concise manner will deliver all the details the reader needs. The most important part of it is a “summary within a summary”: one final sentence which explains why the research is important, and what the article has concluded.

What’s the big deal?

Lay summaries are already commonly used by researchers in many subject areas, as they encourage and increase the possibility of collaboration, and some funding bodies even require them as part of their application procedure. Writing such summaries – distilling your work into a “portable” and maximally-accessible form can bring many benefits for your wider interactions with society at large. Among other things, they’re great for use in press releases or when communicating with journalists. In short: this is a communications skill worth learning.

Here are some pointers on how to write a useful lay summary:

Predict and cover the “so what?” factor – justify your research.

Give some background and context to the research. What prompted you to do it?

Follow a logical order. This may not always coincide with a temporal order.

Explain the impact of the work – what is going to change (especially in relation to wider society)?

Use succinct, short sentences – and write in plain English. Imagine you’re talking to an undergraduate who’s just stepped into your introductory class. Or, better still, pretend you’re trying to explain your article to a distant family member who works in retail/fashion/hospitality.

Avoid jargon unless absolutely necessary and explain it if you do have to keep it in.

Use first person and active voice (“we agreed” rather than “it was agreed”).

Use positives not negative sentences: “You will have repeat appointments at least once a fortnight”, rather than “The usual practice is not to schedule repeat appointments more frequently than once a fortnight”

Images are very important – try to include one if you can.

When you think you’re ready with your summary, ask a friendly non-academic to read it. Ask them if they understood it: the number of questions you get might dictate that further revision is needed!

Supporting lay summaries at Elsevier

Here at Elsevier we’ve been exploring how we can support authors with writing, hosting and promoting lay summaries. Several of the journals we publish including:  Epilepsy & Behavior Case Reports opens in new tab/window ,  International Journal of Paleopathology ,  Journal of Archaeological Science: Reports opens in new tab/window and  Journal of Hepatology opens in new tab/window  now provide lay summaries for selected papers on their homepages. These are made freely available to readers. Note that different journals and subject areas might approach the same basic idea in various ways. For example, the  Materials Today  group of journals has recently launched its “Contributor” project whereby early and mid-career researchers are encouraged to write “news summaries” of recent articles (which are then checked with the original author(s) for accuracy and published on the  Materials Today news page opens in new tab/window ). There might be similar initiatives in your community, so make sure you keep your ear to the ground and get involved if you can.

Looking to the future, we’re also in the process of experimenting with facilitating the submission of lay summaries during the submission process – and aggregating them on a grander scale for authors to aid their discoverability. Stay tuned to hear more on our efforts in this regard.

Lay summaries can be a powerful tool to extend and broaden the impact of your research. Don’t forget that there are a number of other tools available to you as author – check out our  guide to “getting noticed” opens in new tab/window , for example. Have a go at writing a summary for your next article and ask your editor if the journal in question is interested in participating in the lay summaries project. Enjoy making a splash with your next article!

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Christopher Tancock

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Comparison of oral anticoagulants for stroke prevention in atrial fibrillation using the UK clinical practice research Datalink Aurum: A reference trial (ARISTOTLE) emulation study

Emma maud powell.

1 Department of Non-communicable Disease Epidemiology, Faculty of Epidemiology and Population Health, London School of Hygiene and Tropical Medicine, London, United Kingdom

Usha Gungabissoon

2 Epidemiology, GSK, London, United Kingdom

John Tazare

3 Department of Medical Statistics, Faculty of Epidemiology and Population Health, London School of Hygiene and Tropical Medicine, London, United Kingdom

Liam Smeeth

Paris j. baptiste.

4 Clinical Effectiveness Group, Centre for Primary Care, Wolfson Institute of Population Health, Barts and The London School of Medicine and Dentistry, Queen Mary University of London, London, United Kingdom

Turki M. Bin Hammad

5 Methodology and biostatistics team, Department of Efficacy and Safety, Drug sector, Saudi Food and Drug Authority, Riyadh, Saudi Arabia

Angel Y. S. Wong

Ian j. douglas.

6 School of Health and Wellbeing, University of Glasgow, Glasgow, United Kingdom

Associated Data

Data are not publicly available but are available subject to protocol approval via CPRD’s Research Data Governance Process ( https://cprd.com/data-access ) for researchers who meet the criteria for access to confidential data. The data underlying the results presented in the study are available from CPRD ( https://www.cprd.com ).

Stroke prevention guidance for patients with atrial fibrillation (AF) uses evidence generated from randomised controlled trials (RCTs). However, applicability to patient groups excluded from trials remains unknown. Real-world patient data provide an opportunity to evaluate outcomes in a trial analogous population of direct oral anticoagulants (DOACs) users and in patients otherwise excluded from RCTs; however, there remains uncertainty on the validity of methods and suitability of the data.

Successful reference trial emulation can support the generation of evidence around treatment effects in groups excluded or underrepresented in trials.

We used linked United Kingdom primary care data to investigate whether we could emulate the pivotal ARISTOTLE trial (apixaban versus warfarin) and extend the analysis to investigate the impact of warfarin time in therapeutic range (TTR) on results.

Methods and findings

Patients with AF in the UK Clinical Practice Research Datalink (CPRD Aurum) prescribed apixaban or warfarin from 1 January 2013 to 31 July 2019 were selected. ARISTOTLE eligibility criteria were applied to this population and matched to the RCT apixaban arm on baseline characteristics creating a trial-analogous apixaban cohort; this was propensity-score matched to warfarin users in the CPRD Aurum. ARISTOTLE outcomes were assessed using Cox proportional hazards regression stratified by prior warfarin exposure status during 2.5 years of patient follow-up and results benchmarked against the trial results before treatment effectiveness was further evaluated based on (warfarin) TTR.

The dataset comprised 8,734 apixaban users and propensity-score matched 8,734 warfarin users. Results [hazard ratio (95% confidence interval)] confirmed apixaban noninferiority for stroke or systemic embolism (SE) [CPRD 0.98 (0.82,1.19) versus trial 0.79 (0.66,0.95)] and death from any cause [CPRD 1.03 (0.93,1.14) versus trial 0.89 (0.80,0.998)] but did not indicate apixaban superiority. Absolute event rates for stroke/SE were similar for apixaban in CPRD Aurum and ARISTOTLE (1.27%/year), whereas a lower event rate was observed for warfarin (CPRD Aurum 1.29%/year, ARISTOTLE 1.60%/year).

Analysis by TTR suggested similar effectiveness of apixaban compared with poorly controlled warfarin (TTR < 0.75) for stroke/SE [0.91 (0.73, 1.14)], all-cause death [0.94 (0.84, 1.06)], and superiority for major bleeding [0.74 (0.63, 0.86)]. However, when compared with well-controlled warfarin (TTR ≥ 0.75), apixaban was associated with an increased hazard for all-cause death [1.20 (1.04, 1.37)], and there was no significant benefit for major bleeding [1.08 (0.90, 1.30)]. The main limitation of the study’s methodology are the risk of residual confounding, channelling bias and attrition bias in the warfarin arm, and selection bias and misclassification in the analysis by TTR.

Conclusions

Analysis of noninterventional data generated results demonstrating noninferiority of apixaban versus warfarin consistent with prespecified benchmarking criteria. Unlike in ARISTOTLE, superiority of apixaban versus warfarin was not seen, possible due to the lower proportion of Asian patients and higher proportion of patients with well-controlled warfarin compared to ARISTOTLE. This methodological template can be used to investigate treatment effects of oral anticoagulants in patient groups excluded from or underrepresented in trials and provides a framework that can be adapted to investigate treatment effects for other conditions.

Emma Maud Powell and colleagues use target trial emulation to demonstrate how real world data can extend our knowledge of anticoagulation treatment effects using non-interventional methods.

Author summary

Why was this study done.

• Stroke prevention treatment guidelines for patients with atrial fibrillation (AF) are based on results from randomised controlled trials (RCTs); we do not know if these results are relevant to patients that would not have been eligible to be included in the RCTs.
• This study used routinely collected health data from the United Kingdom to emulate an RCT that compared apixaban to warfarin, ARISTOTLE, and also looked at whether the benefit of apixaban compared with warfarin was impacted by the quality of warfarin therapy (measured by time in therapeutic range (TTR)).
• Emulating an RCT for stroke prevention in patients with AF should help to understand how transferable RCT results are to “real-world” practices and whether this methodological approach can help to improve treatment options and outcomes for patient groups currently underrepresented in clinical trials.

What did the researchers do and find?

• The researchers looked at patients with AF in a UK primary care data prescribed apixaban or warfarin and applied a “reference trial emulation” approach, in which the ARISTOTLE trial eligibility, selection, and analysis approaches were applied to UK primary care data and results benchmarked against those of ARISTOTLE.
• Patients prescribed apixaban had similar rates of outcomes to those prescribed warfarin in our cohort, and our results were successfully benchmarked against ARISTOTLE. Unlike ARISTOTLE, we did not see superiority of apixaban versus warfarin [hazard ratio (95% confidence interval)] for time to stroke or systemic embolism: 0.98 (0.82,1.19) in our cohort versus 0.79 (0.66,0.95) in ARISTOTLE.
• We also found the benefit of apixaban versus warfarin differed for some outcomes depending on the quality of warfarin therapy with apixaban (i) superior only to poorly controlled warfarin therapy for major bleeding [TTR < 0.75: 0.74 (0.63, 0.86), TTR ≥ 0.75: 1.08 (0.90, 1.30)] (ii) associated with an increased risk of death compared only to well-controlled warfarin therapy [TTR ≥ 0.75: 1.20 (1.04, 1.37), TTR < 0.75: 0.94 (0.84, 1.06)].

What do these findings mean?

• Our results support the NICE guidelines on selecting treatment for stroke prevention in patients with AF and also provide reassurance on continuing warfarin in patients with high TTR.
• We can use UK primary health care data to emulate a reference trial of treatments for the prevention of stroke in AF.
• We can use the data and methods to look at how well treatments work in patients that would not have been included in RCTs such as those with multimorbidity or patient groups underrepresented in RCTs such as ethnic minority groups and older patients.
• Study limitations include the possibility of residual confounding, a risk patients doing well on warfarin were overrepresented in our cohort, a lower proportion of Asian participants in our cohort compared with ARISTOTLE, and the likelihood of residual selection bias/misclassification in the TTR analysis.

Introduction

Atrial fibrillation (AF) is a common type of cardiac arrhythmia with an estimated prevalence of 3.3% in UK adults aged ≥35 years [ 1 ]. AF is a risk factor for stroke; patients with AF have a 5-fold increased risk of stroke compared with people without AF [ 2 ], and around a quarter of all strokes are attributed to this arrhythmia [ 3 ]. In addition, increased levels of mortality, morbidity, and disability with longer hospital stays are observed in stroke patients with AF compared with stroke patients without AF [ 4 , 5 ].

Pharmacological therapy recommended to reduce the risk of stroke in AF includes the use of oral anticoagulants (OACs). The introduction of direct oral anticoagulants (DOACs) for AF since 2012 in the United Kingdom provided a choice of treatment alongside the older OAC class of vitamin K antagonists (VKAs), such as warfarin, which has been available for over 60 years. The VKA OACs require regular monitoring of international normalised ratio (INR) to keep patients in the optimal therapeutic range (typically 2.0 to 3.0) in which risk of both ischemic and bleeding events are minimised [ 6 ]. A patient may require dose adjustments to stay within their INR target range. A key measure of quality of warfarin treatment is, therefore, the time in therapeutic range (TTR), which estimates the proportion of time a patient has spent with INR within optimal range. A TTR of 0.75 or greater is often considered as indicating optimal INR control and suggests a patient is spending a high proportion of their time in their INR target range.

ARISTOTLE was a pivotal randomised controlled trial (RCT) of the DOAC apixaban designed to demonstrate noninferiority compared with warfarin in the prevention of stroke or systemic embolism (SE) in patients with AF. The results demonstrated superiority of apixaban over warfarin for both prevention of stroke/SE and safety (major bleeding) [ 7 ]. Results in the European Union patient subset from the trial suggested the observed superiority of apixaban might be dependent on how well warfarin therapy was managed in the comparator group [ 8 ], an analysis that has not yet been performed outside of trial settings. In the National Institute for Health and Care Excellence (NICE) review of ARISTOTLE, several professional groups noted the TTR of warfarin users in ARISTOTLE may be lower than what is typical in UK clinical practice [ 9 ].

Treatment guidelines for DOACs are based on evidence from RCTs; however, it is unclear whether these results extend to patient groups typically excluded from trials such as those with increased bleeding risk or severe comorbidities. While there have been a number of previous studies of DOAC effectiveness using noninterventional data, there remains uncertainty on whether the data sources and methods used have fully accounted for the lack of treatment randomisation and issues such as selection bias and confounding. Comparing results from real-world studies with RCT results is challenging due to differences in patient populations, treatment adherence, and study design. However, reference trial emulation involves use of an existing named RCT to (1) inform observational study design and (2) benchmark results against, providing confidence in validity of the selected observational methods and data [ 10 – 13 ]. The noninterventional analysis methods can then be applied, under a set of assumptions, to reliably estimate effects in groups of patients with AF who would have been excluded from (or underrepresented in) the reference trial [ 14 ] such as patients aged >80 that were underrepresented in ARISTOTLE compared with patients with AF in UK clinical practice and patients with increased bleeding risk that were excluded by the trial eligibility criteria.

There is increasing interest in trial emulation using observation data and in the application of recent developments in pharmacoepidemiology methods involving the inclusion of prevalent users. This study used a framework that involved coarsened exact matching to select patients matching the trial population on aggregate, and sampling of prevalent users in a way that avoids selection bias and emulates the process of screening into an RCT, to construct a cohort of patients similar to the target trial population that included both new and prevalent users. This methodological approach could be adapted to a variety of treatments and different therapeutic areas.

This study sought to (1) create an ARISTOTLE-analogous cohort using routinely collected primary and secondary care data in the UK, (2) benchmark results obtained in the ARISTOTLE-analogous cohort with ARISTOTLE results, and (3) explore whether apixaban treatment-effects in clinical practice are influenced by how well warfarin therapy is controlled.

Materials and methods

This study is reported as per the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) guideline ( S1 STROBE Checklist).

Study design

A propensity score (PS) matched cohort study with emulation of a reference trial (ARISTOTLE).

Setting/data sources

Uk electronic healthcare records.

This study used noninterventional data from UK Clinical Practice Research Datalink (CPRD) Aurum, a database containing anonymised data from 738 primary care practices across England (approximately 13% of the population of England with 19 million patient records and 7 million active as of September 2018 [ 15 ]). CPRD Aurum contains information on clinical diagnoses, prescribing, referrals, tests, and demographic/lifestyle factors and is representative of the population of England in geographical spread, social deprivation, age, and sex [ 15 ]. This study also used 2 additional data sources linked to CPRD Aurum: Hospital Episodes Statistics (HES) data, which contain data on patients admitted to NHS hopsitals including diagnoses, admission, and discharge, and Office of National Statistics (ONS) mortality data.

The reference trial (ARISTOTLE)

ARISTOTLE was a randomised, double-blind trial completed in 2011, comparing apixaban with warfarin in the prevention of stroke and SE. The trial included 18,201 patients with AF and at least 1 additional risk factor for stroke. The trial was designed to test for noninferiority of apixaban compared with warfarin (noninferiorirty margin of 1.38 for the upper limit of the 95% CI of the hazard ratio (HR) for the primary outcome) and showed apixaban superiority for (1) the primary outcome of stroke or SE (HR 0.79; 95% CI 0.66, 0.95), (2) the safety endpoint of major bleeding (HR 0.69; 95% CI 0.60, 0.80), and (3) death from any cause (HR 0.89; 95% CI 0.80, 0.99). The ARISTOTLE findings led to the NICE guidelines on stroke prophylaxis in patients with AF recommending apixaban as a treatment.

ARISTOTLE eligibility criteria and summary baseline patient characteristics were used to select a cohort of patients from CPRD Aurum analogous to the ARISTOTLE participants.

The use of CPRD and ARISTOTLE are described in a previous publication [ 14 ], and the use of CPRD for this project was approved by the MHRA Independent Scientific Advisory Committee ( S1 ISAC Protocol). All data used in this study were anonymised.

Diagnostic and therapeutic codelists

All diagnostic and therapeutic codelist files used are available at https://datacompass.lshtm.ac.uk/id/eprint/3590/ .

Patient selection

Step 1: application of trial eligibility criteria to patients in cprd.

We first selected HES-linked patients registered in CPRD Aurum between 1 January 2013 and 31 July 2019, who had at least 6 months between registration and the index date. ARISTOTLE recruited both new (warfarin-naïve) and prevalent (warfarin-experienced) users of warfarin with randomisation stratified on prior warfarin (or other VKA) exposure status (warfarin naïve or experienced). To be classified as warfarin-naïve patients were required to have no evidence of exposure to warfarin or other VKA in the 5 years prior to the index date. To enable selection of a similar cohort of patients in CPRD Aurum (including both new and prevalent users of warfarin), the following process was used in determining index date:

- apixaban users

index date = first prescription of apixaban in the study period;

apixaban user classified as warfarin-naïve or warfarin-experienced at this date

- warfarin users

for new users of warfarin: index date = first prescription of warfarin in the study period;

for prevalent users of warfarin: a pool of potential index dates was selected containing all prescription dates in the study period, with index date selected at the later treatment-history sampling stage (see step 3).

ARISTOTLE eligibility criteria (Table A2 in S1 Appendix ) [ 7 ] were applied giving a trial-eligible cohort for apixaban users, a trial-eligible cohort of new users of warfarin, and a pool of potential index dates (with all potential index dates kept in regardless of ARISTOTLE eligibility at this stage) for warfarin continuers (prevalent warfarin users).

Step 2: Selection of apixaban trial-analogous patients in CPRD

We selected a subset of the CPRD Aurum trial-eligible apixaban patients that better matched the ARISTOTLE apixaban participants based on aggregate summaries for the following key ARISTOTLE baseline characteristics:

• Congestive heart failure or left ventricular systolic dysfunction
• Hypertension requiring treatment
• Diabetes mellitus
• Prior stroke/transient ischaemic attack (TIA)/SE
• Level of renal impairment
• Prior VKA/warfarin exposure

To characterise the baseline patient characteristics of ARISTOTLE, we used the key publication of the trial results [ 7 ], discussion of trial results by regulatory bodies [ 8 , 9 , 16 ], and publications on the trial presenting cross-tabulations on key characteristics [ 17 , 18 ].

An ARISTOTLE-analogous cohort of CPRD Aurum apixaban patients was then selected using a modified form of coarsened exact matching [ 19 ] (see S1 Appendix for details).

Step 3: Matching of apixaban trial-analogous patients to warfarin trial-eligible patients in CPRD

To emulate ARISTOTLE, which stratified randomisation on prior VKA exposure status, patients in the CPRD cohort were matched separately within the VKA-naïve and VKA-experienced strata. A 3-step procedure, based on methods proposed by Suissa and colleagues [ 20 ] and Webster-Clark and colleagues [ 21 ], was used to select and match patients in the VKA-experienced strata while avoiding selection bias; this procedure is summarised in Fig 1 and described in S1 Appendix .

CPRD, Clinical Practice Research Datalink; RCT, randomised controlled trial; VKA, vitamin K antagonist.

The trial-analogous CPRD Aurum apixaban patients were matched to warfarin CPRD Aurum patients using greedy nearest-neighbour matching on the logit of the PS; a caliper of 0.2 times the standard deviation of the logit of the PS was used for matching as recommended by Austin [ 22 ].

The covariates included in the PS models are detailed in Table 1 .

ACEI, angiotensin-converting enzyme inhibitor; AF, atrial fibrillation; ARB, angiotensin receptor blocker; COPD, chronic obstructive pulmonary disease; GP, general practicioner; NSAID, nonsteroidal anti-inflammatory drug; PS, propensity score; SE, systemic embolism; TIA, transient ischemic attack.

The model resulting in the most balanced cohort was chosen with balance assessed by looking at standardised differences across all variables after matching using a target threshold of 0.05 for the maximum difference allowed for any individual variable. Balance of covariates considered to be most important in predicting outcome were prioritised, namely, age, sex, and stroke risk factors.

Exposures and outcomes

Exposure to apixaban (5 mg/2.5 mg) or warfarin was determined using CPRD prescribing records with no restrictions on the dose prescribed.

The primary effectiveness outcome was the composite of stroke (ischemic or haemorrhagic) or SE; individual components of this outcome (stroke, ischemic or uncertain type of stroke, haemorrhagic stroke, SE) and death from any cause were the key secondary effectiveness outcomes. Secondary effectiveness outcomes included myocardial infarction (MI), pulmonary embolism or deep vein thrombosis, and composite endpoints of effectiveness outcomes. The primary safety outcome was major bleeding (including by location—intracranial, gastrointestinal, or other location such as urinary or gynaecological). All outcomes involved hospitalisation or death and were ascertained using HES and ONS data. The ICD-10 codes used in ascertaining stroke occurrence have been recommended as having high positive predictive value [ 23 ].

Statistical analysis

Methods of analysis.

A prospective protocol was published prior to the analysis detailing the planned analyses ([ 14 ]; also in S1 Appendix ).

Changes from the planned protocol are described in Table 2 .

CPRD, Clinical Practice Research Datalink; HR, hazard ratio; INR, international normalised ratio; IQR, interquartile range; PS, propensity score; TTR, time in therapeutic range; VKA, vitamin K antagonist.

All time-to-event endpoints were analysed using a Cox proportional hazards model, stratified by prior VKA status (experienced, naïve). The effectiveness outcomes were analysed using the intention-to-treat principle, and major bleeding was analysed using an on-treatment censoring scheme. Patients were censored at 2.5 years after index date reflecting typical maximum duration of follow-up in ARISTOTLE. Cluster-robust standard errors were used with pair membership as the clustering variable [ 24 , 25 ]. The proportional hazards assumption was assessed by looking at the log-log of the Kaplan–Meier survival curves and inspection of scaled Schoenfeld residuals plotted against time. Analyses were performed using SAS version 9.4 and R version 4.2.1.

Supplementary analyses

A protocol planned analysis in the subset of patients deemed adherent (with adherence measured by TTR in the warfarin users and by proportion of days covered by prescriptions in the apixaban users) was planned to assess the impact of adherence on outcomes. The planned analysis was not possible due to the apixaban prescription data not providing a useful measure of adherence. An analysis by INR TTR was performed instead to assess the impact of warfarin control on results with all outcomes analysed by TTR (TTR < 0.75 and TTR ≥ 0.75). Individual predicted TTR based on baseline variables was used for patients missing TTR. In order to perform the TTR analysis while maintaining balance in the baseline covariates, inverse probability treatment weighting (IPTW) was used to rebalance the baseline characteristics, applying stabilised weights to the ARISTOTLE-analogous apixaban users. A similar approach to the main analysis was used with PS models constructed separately for the new users and warfarin-experienced users.

An additional post hoc analysis was performed looking at the proportion of apixaban patients prescribed reduced-dose apixaban along with a comparison of the patients meeting the criteria for dose-reduction against the dose actually prescribed. In this analysis, apixaban dose in the ARISTOTLE-analogous CPRD cohort was assessed and compared against the ARISTOTLE protocol-specified criteria and NICE criteria for reduced apixaban dose. ARISTOTLE specified that participants meeting any 2 of the following criteria assessed at the time of randomisation should have their apixaban dose reduced to 2.5 mg BID: age ≥80 years, body weight ≤60 kg, or serum creatinine ≥1.5 mg/dL. These criteria are equivalent to the NICE guidelines for dose reduction with NICE having an additional criteria indicating reduced dose in those with creatinine clearance 15 to 29 mL/minute.

In addition, to assess the impact of the quality of dose-adjustment in the CPRD cohort on the observed effectiveness of apixaban relative to warfarin, a supplementary post hoc analysis was performed looking at the results in the subset of apixaban patients prescribed the correct dose compared with IPTW rebalanced warfarin comparators.

Sensitivity analyses

Primary and secondary effectiveness outcomes were also analysed using the on-treatment censoring scheme to investigate whether treatment discontinuation compromises confidence in the effectiveness analyses.

Treatment persistence was defined by looking at longitudinal prescription data for OACs; OAC treatment windows were derived in which gaps > = 6 months between prescription dates were considered as distinct treatment windows. The end of each OAC treatment window was derived as the date of the last prescription of index OAC + the number of days supply given in the last prescription + a grace period of 30 days. In cases of overlapping OAC treatment windows, the date of the first prescription of the subsequent OAC treatment window was used to define the end of the prior OAC window. A prescription for a different OAC from the index OAC treatment was considered as a treatment switch. An ending of index OAC treatment with no subsequent prescription for any other OAC recorded was considered as treatment stop. Gaps of > = 6 months with no subsequent OAC prescriptions recorded were categorised as having stopped OAC treatment.

The set of patients who switched or discontinued treatment during follow-up were examined to ascertain whether selection bias due to attrition may have affected the on-treatment analyses (Table A9 in S1 Appendix ).

Apixaban was first launched for AF in the UK in January 2013, with relatively few patients receiving a prescription in the first year it was available; we therefore performed a sensitivity analysis with the start of study period shifted forwards a year to investigate the impact of inclusion of early adopters who may differ from later adopters of a new drug.

Confounding and bias

In the study period, apixaban was a newly available treatment leading to the possibility of channelling bias [ 26 ]. By applying trial eligibility criteria to both treatment cohorts and matching using baseline covariates, we aimed to minimise channelling bias. To handle confounding, treatment arms were matched using propensity score matching (PSM) [ 27 ].

Benchmarking results against ARISTOTLE

The study hypothesis was that results in the CPRD ARISTOTLE-analogous cohort would be comparable to the ARISTOTLE results, as defined by the prespecified benchmarking criteria. A slightly weaker benefit of apixaban versus warfarin was expected based on the weaker benefit seen in the EU subgroup of ARISTOTLE, and an expectation that the quality of warfarin control in UK patients may be higher than that observed in ARISTOTLE.

The benchmarking criteria for considering the results in the trial-analogous CPRD cohort to be comparable with ARISTOTLE were prespecified and published previously [ 14 ]:

• The effect size must be clinically comparable with the ARISTOTLE findings; the HR for time to stroke/SE with the HR must be between 0.69 and 0.99. This range is not symmetrical around the ARISTOTLE estimate of 0.79 as it is anticipated the treatment effect in routine clinical care may be weaker than that seen in the optimised setting of a clinical trial.
• The upper limit of the 95% CI for the HR for time to stroke/SE must be less than 1.38 (noninferiority margin used in ARISTOTLE, updated since protocol—see Table 2 ).

The benchmarking step applied only to the primary effectiveness outcome in the trial-analogous CPRD cohort; results in other groups such as patients underrepresented or excluded from the trial would not necessarily be expected to remain consistent to the RCT results, given the relative risks may differ in these groups. Comparability of other outcomes was to be assessed descriptively with no formal criteria or hypothesis testing used.

Missing data

Patients with missing systolic blood pressure (0.1%), body mass index (3.3%), smoking status (0.1%), or socioeconomic status (0.1%) were excluded from the trial-eligible cohort as the proportion of patients with these missing was low. Patients with missing renal function (1.3%), ethnicity (0.4%), or alcohol use (5.6%) were kept in the cohort through a missing indicator approach; this approach is valid under the assumption that these variables act as confounders and influence clinician prescribing decisions only when observed [ 28 ]. A total of 1,176 (13.3%) warfarin users in the CPRD cohort did not have INR measurements in the data during their treatment period with predicted TTR used for these patients in the analysis by TTR (see S1 Appendix for details).

Scientific approval was provided by the London School of Hygiene and Tropical Medicine research ethics committee (ref 17682) and the independent scientific advisory committee of the Medicines and Healthcare Products Regulatory Agency (protocol no. 19_066R). CPRD data are already approved via a national research ethics committee for purely noninterventional research of this type. CPRD data are analysed anonmymously; therefore, individual patient consent is not sought by contributing medical practices when data are shared with CPRD; however, patients are able to opt out of their patient information being shared for research.

Participants

Between 1 January 2013 and 31 July 2019, there were 86,888 people with AF prescribed apixaban and 159,632 prescribed warfarin in HES-linked CPRD Aurum practices ( Fig 2 ). Application of minimum registration period and ARISTOTLE inclusion criteria reduced this to 67,539 apixaban and 139,527 warfarin patients. After applying ARISTOTLE exclusion criteria, there were 41,487 apixaban and 101,159 warfarin patients.

Flow of number of individuals included in the analysis. AF, atrial fibrillation; ALT, alanine transaminase; AST, aspartate transaminase; BMI, body mass index; BP, blood pressure; CPRD, Clinical Practice Research Datalink; HES, Hospital Episodes Statistics; Rx, Prescription; SES, socioeconomic status; ULN, upper limit of normal; VKA, vitamin K antagonist. a Severe comorbid condition with life expectancy <1 year or reasons making participation impractical; b ALT or AST > 2X ULN or Total Bilirubin ≥ 1.5X ULN; c Pregnant or breastfeeding within 3 years prior. See Table A1 in S1 Appendix for detailed list of inclusion and exclusion criteria. Note: For prevalent warfarin users, trial eligibility only revealed at point of random selection into the cohort for prevalent users. Numbers in figure show maximum theoretical number of warfarin users available should they be selected only at a time they were eligible for the trial.

Selecting apixaban patients to match ARISTOTLE on key baseline characteristics yielded 9,120 apixaban patients (3,912 new users and 5,208 prevalent users) available for PSM to 101,159 warfarin patients. For 274 apixaban patients, no match could be found giving a PS matched cohort of 8,846 apixaban and 8,846 warfarin patients.

Application of ARISTOTLE inclusion/exclusion criteria and matching to ARISTOTLE

Applying the ARISTOTLE inclusion/exclusion criteria and matching to ARISTOTLE baseline patient characteristics resulted in a cohort similar to the ARISTOTLE apixaban participants ( Table 3 ); for example, median age was 78 and mean CHADS 2 score 2.4 in CPRD Aurum before applying trial criteria and matching, whereas the median age of 71 and mean CHADS 2 score 2.1 after these steps matched the ARISTOTLE apixaban participants. The ARISTOTLE-analogous apixaban arm matched the trial arm on prior VKA exposure, age, sex, stroke risk factors and CHADS 2 score, and proportion of patients with moderate or severe renal impairment.

ACE, angiotensin-converting enzyme; ARB, angiotensin-receptor blocker; BMI, body mass index; CHADS 2 , stroke risk factor score based on congestive heart failure, hypertension, age ≥75 years, diabetes, prior stroke; CPRD, Clinical Practice Research Datalink; IMD2015, Index of Multiple Deprivation 2015; imp., impairment; IQR, interquartile range; LVEF, left ventricular ejection fraction; MI, myocardial infarction; PSM, propensity score matching; SD, standard deviation; SE, systemic embolism; TIA, transient ischemic attack; VKA, vitamin K antagonist.

Differences remained on baseline characteristics it was not feasible to match on, namely, ethnicity (95.2% white, 2.4% Asian in CPRD Aurum apixaban versus 82.6% white, 14.4% Asian in ARISTOTLE) and concomitant medications (amiodarone 3.8%, aspirin 5.8%, digoxin 13.9% in CPRD Aurum apixaban users versus amiodarone 11.1%, aspirin 31.3%, digoxin 32.0% in ARISTOTLE apixaban arm). See S1 Appendix for details on matching feasibility.

Propensity score matching of CPRD Aurum trial-analogous apixaban users to CPRD Aurum warfarin users

Results of propensity score matching.

Before PSM, differences between treatment groups were evident for most baseline variables including age (median age 71 in apixaban versus 78 in warfarin), sex (apixaban 35.6% female versus warfarin 43.6%), and stroke risk factors (see Table 3 ). After PSM, all baseline characteristics were well balanced (maximum standardised difference .031). From 9,120 apixaban users, only 274 (3.0%) were dropped due to unsuccessful matching.

Main results

The HR for stroke/SE in the PS matched groups was 0.98 (95% CI 0.82,1.19) ( Fig 3 and Table A3 in S1 Appendix ). This association was consistent with the noninferiority margin (upper limit of the 95% CI less than 1.38) [ 7 ] but did not show superiority as predicted by ARISTOTLE [HR 0.79 (95% CI 0.66,0.95)] ( Fig 3 and Table A2 in S1 Appendix ). The outcome of all-cause mortality also showed noninferiority [Aurum 1.03 (0.93,1.14) versus trial 0.89 (0.80,0.998)] but did not indicate apixaban superiority. Absolute event rates for the primary outcome and components were close to the trial for apixaban—for example [comparing Aurum versus trial], stroke/SE event rate of 1.27%/year versus 1.27%, whereas the warfarin group had a lower event rate compared with ARISTOTLE (stroke/SE event rate of 1.29%/year versus 1.60% and hemorrhagic stroke 0.33%/year versus 0.47%/year) ( Fig 3 ). Mean duration of follow-up in the cohort was 1.8 years in the apixaban arm and 2.2 years in the warfarin arm.

warfarin. Absolute event rates (%/year) and HR (95% CIs) are presented for key effectiveness outcomes in (i) ARISTOTLE, (ii) CPRD Aurum trial-matched cohort, (iii) CPRD Aurum trial-matched with TTR < 0.75, and (iv) CPRD Aurum trial-matched with TTR ≥ 0.75. Dashed line shows noninferiority margin 1.38 for the upper bound of the 95% CI of the HR used in ARISTOTLE for the primary outcome of stroke or SE. For the analysis by TTR, IPTW was applied to the apixaban users targeting the treatment effect in the warfarin users with TTR < 0.75 and TTR ≥ 0.75. CI, confidence interval; CPRD, Clinical Practice Research Datalink; HR, hazard ratio; IPTW, inverse probability treatment weighting; SE, systemic embolism; TTR, time in therapeutic range.

Analysis of impact of warfarin time in therapeutic range (TTR)

TTR was higher in the CPRD cohort than in ARISTOTLE (mean 0.73 versus 0.62, median 0.76 versus 0.66).

Analysis by TTR suggested noninferiority of apixaban versus warfarin in those with TTR < 0.75 [stroke/SE 0.91 (0.73,1.14), all-cause death 0.94 (0.84, 1.06)] ( Fig 3 ). Apixaban was associated with similar hazards for stroke by category of TTR and increased hazards of death compared to warfarin in those with well-controlled warfarin treatment (TTR ≥ 0.75) [stroke/SE 1.05 (0.82, 1.34), all-cause death 1.20 (1.04, 1.37)] ( Fig 3 ).

Analysis of apixaban dose-adjustment

The proportion of patients meeting the criteria for reduced dose apixaban ( Table 4 ) was similar between the CPRD ARISTOTLE-analogous apixaban, warfarin, and RCT apixaban groups (4.9%, 4.9%, and 4.7%, respectively). When including the additional NICE criteria of creatinine clearance, 5.1% of apixaban users in the ARISTOTLE-analogous cohort had an indication for reduced-dose apixaban, yet a larger proportion (14.3%) were prescribed reduced dose apixaban implying some patients in CPRD Aurum may have been prescribed the wrong dose and/or information on criteria for dose reduction may have been missing from CPRD Aurum.

NICE criteria for dose-adjustment included additional criteria of creatinine clearance 15–29 mL/minute.

CPRD, Clinical Practice Research Datalink; N/A, not applicable; NICE, National Institute for Health and Care Excellence; NR, not reported; RCT, randomised controlled trial.

A futher analysis of the quality of dose-adjustment in patients in CPRD Aurum ( Table 5 ) indicated 10.5% of patients may have been prescribed an incorrect dose of apixaban at the index prescription based on the data contained in their electronic health records (EHRs). The majority of incorrect dose relating to patients being prescribed reduced-dose apixaban despite not meeting the criteria for dose reduction. A large proportion of patients prescribed an incorrect dose had only 1 dose adjustment criteria (59.6% of those with incorrect dose), suggesting some prescribers may have thought a dose reduction was warranted when only 1 criteria was present. Other possible reasons for the incorrect dose-adjustment observed here may be data on the criteria missing from the EHR (i.e., incorrect ascertainment) or consideration of other medical history that made a prescriber adjust the dose.

To assess the impact of the quality of dose-adjustment in the CPRD cohort on the effectiveness of apixaban, a supplementary post hoc analysis was performed looking at the results in the subset of apixaban patients prescribed the correct dose ( N = 7,921) compared with IPTW rebalanced warfarin comparators. The results in this subset were consistent with the primary results showing apixaban to be noninferior to warfarin (stroke/SE 0.96 [0.78,1.17], death 0.97 [0.87,1.09]) with the results moving slightly closer to those observed in ARISTOTLE.

Safety results

The analysis for safety outcomes is presented in Fig 4 and Table A5 in S1 Appendix ; patients on apixaban had a lower risk of major bleeding compared with those on warfarin, HR (95% CI) 0.88 (0.77,1.00), consistent with ARISTOTLE. Analysis by TTR suggested superiority of apixaban for major bleeding in those with TTR <0.75 [0.74 (0.63, 0.86)], whereas apixaban users had a similar risk of major bleeding compared with those with optimal warfarin control (TTR ≥ 0.75) [1.08 (0.90,1.30)].

warfarin. Absolute event rates (%/year) and HR (95% CIs) are presented for key safety outcomes in (i) ARISTOTLE, (ii) CPRD Aurum trial-matched cohort, (iii) CPRD Aurum trial-matched with TTR < 0.75, and (iv) CPRD Aurum trial-matched with TTR ≥ 0.75. For the analysis by TTR, IPTW was applied to the apixaban users targeting the treatment effect in the warfarin users with TTR <0.75 and TTR ≥0.75. CI, confidence interval; CPRD, Clinical Practice Research Datalink; HR, hazard ratio; IPTW, inverse probability treatment weighting; TTR, time in therapeutic range.

Table A7 in S1 Appendix shows the proportion of patients switching treatment. A higher proportion of patients on warfarin switched to an alternative OAC during follow-up compared with those on apixaban (16.3% versus 6.1%).

Comparing patients who switched treatment during follow-up with those that continued on index treatment (Table A8 in S1 Appendix ) suggests possible selection bias due to attrition in on-treatment analyses with median TTR markedly lower in warfarin users who switched treatments compared with persistent warfarin users (median TTR 0.64 versus 0.78). On-treatment analyses would likely be biased against apixaban since patients doing badly on warfarin (i.e., with low TTR) who would be more likely to experience events in the warfarin arm would be censored at treatment switch.

On-treatment analyses censoring around treatment switch or discontinuation are presented for the effectiveness analyses in the appendix (Table A6 in S1 Appendix ); the results show evidence of the expected attrition bias against apixaban when compared with the ITT results in Fig 2 , for example, HR for stroke/SE is 1.04 (0.86, 1.25) in the on-treatment compared with 0.98 (95% CI 0.82, 1.19) in the ITT analysis.

Repeating the analysis with start of study period shifted forwards a year to investigate the impact of inclusion of early adopters yielded similar results to the primary analysis (Table A9 in S1 Appendix ).

Prior INR control was not included in the PS models for the VKA-experienced due to a high rate of missing prior INR data (missing for 34% in the apixaban arm). A post hoc sensitivity analysis including a prior INR control variable in the PSM gave results consistent with the primary results [stroke/SE HR 95% CI 1.02 (0.86,1.21)]. Details of this post hoc analysis are in S1 Appendix .

In our emulation of ARISTOTLE using UK routinely collected healthcare data, we found results that met our predefined criteria for comparability with the trial. We saw noninferiority of apixaban versus warfarin for prevention of stroke or SE, all-cause mortality, and major bleeding but did not see superiority of apixaban versus warfarin for these outcomes as was seen in ARISTOTLE. We found higher TTR in the patients using warfarin in our cohort compared with the warfarin arm of ARISTOTLE (median 0.76 versus 0.66). While our analysis by TTR showed noninferiority of apixaban versus warfarin for our stroke or SE outcome, we observed an increased risk of death on apixaban compared with patients well-controlled on warfarin (TTR ≥ 0.75) but not when compared with those on poorly controlled warfarin (TTR < 0.75). For major bleeding, while apixaban was superior when compared to those on poorly controlled warfarin, there was no difference when compared to those on well-controlled warfarin. We saw evidence suggesting suboptimal dosing of apixaban in our cohort with approximately 10% of patients in the apixaban arm prescribed the reduced dose without meeting the criteria for the reduced dose.

We found the differences in the overall treatment-effect estimates between our cohort and ARISTOTLE may be explained by the lower proportion of Asian patients in our cohort, differences in INR control in the warfarin arm of our cohort compared with ARISTOTLE, and the higher proportion of patients prescribed a reduced dose of apixaban in our cohort compared with ARISTOTLE.

Our findings are consistent with a UK study of ischemic stroke, which compared DOACs with warfarin [ 29 ]. A Danish study found similar results to ours for stroke/SE [ 30 ], although they found apixaban users had a lower risk of death; a study of US claims data [ 31 ] also found apixaban was associated with a lower risk of death. A systematic review and meta-analysis of 16 studies [ 32 ] found pooled results for stroke and intracranial haemorrhage that were consistent with ours. One study (in US claims data) also aimed to replicate ARISTOTLE [ 33 , 34 ] and, in contrast to our study, found superiority for apixaban for stroke/SE, which may be linked to population differences such as lower TTR in US patients on warfarin [ 35 ] and differences in ethnicity. None of these studies matched to the ARISTOTLE trial participants, included prevalent users, or looked at how warfarin control impacted results. Further details on these studies including design and key results are summarised in Table A10 in S1 Appendix .

A key strength of our study was the use of a framework that sampled prevalent users (the continuing users of warfarin in this study) in a way that avoided selection bias facilitating the construction of a cohort of patients similar to the target trial population, which included both new users of apixaban and warfarin (VKA-naïve) and patients with prior VKA exposure (VKA-experienced) that were randomised to stay on warfarin or switch to apixaban. The use of PSM, stratified by treatment history, enabled us to select a matched cohort well balanced on important covariates. The successful emulation of ARISTOTLE by our study shows that valid treatment effects can be obtained for important outcomes with OACs using noninterventional methods with routinely collected clinical data. Having validated this framework, in future studies, we can look at the effectiveness of OACs in AF patient groups not included or underrepresented in the RCT, such as elderly patients and those at increased bleeding risk. We also recommend future analyses with an extended follow-up period compared with this study to compare the long-term outcomes seen in the noninterventional cohort with projected long-term outcomes from the RCT.

An additional strength of our study was the ability to explore the quality of warfarin treatment in our cohort and the impact of INR control on the treatment effect estimates. Our finding that the benefits of apixaban versus warfarin for some outcomes depended on the quality of INR control in the warfarin arm answers questions raised in the NICE premeeting briefing, which looked at apixaban in the NVAF population and noted the TTR seen in ARISTOTLE “may be lower than what is typical in UK clinical practice” and “apixaban compared with well-controlled warfarin (TTR 75% or more) may not be superior in the long term” [ 8 ]. ARISTOTLE presented outcomes by centre (for example, hospital) TTR quartile and did not show a signal of treatment efficacy differing by centre TTR quartile. We were able to use IPTW to estimate the treatment effect in the different warfarin TTR groups and used predicted TTR for warfarin users missing TTR to attempt to limite the risk of selection bias.

While our study aimed to emulate ARISTOTLE using suitable methods, there were several limitations. Some of the criteria assessed for ARISTOTLE eligibility may not be well recorded in CPRD leading to a risk of misclassification. Furthermore, misclassification of ARISTOTLE eligibility criteria and baseline covariates could be differential by treatment in the VKA-experienced patients if criteria such as renal function are more likely to be checked before changing treatment. However, the most important risk factors for the primary outcome of stroke (the components of CHA 2 DS 2 -VASc stroke risk score) are mostly well recorded in CPRD Aurum and HES.

Our cohort did not attempt to match the trial on the use of concomitant medications in order for our cohort to reflect typical UK prescribing. In ARISTOTLE, 31% of participants were using aspirin and 11% using amiodarone at baseline, whereas in our cohort, only 6% were recorded as using aspirin and 4% amiodarone. Amiodarone potentiates the effects of warfarin, and concomitant use of amiodarone with DOACs is associated with increased risk of major bleeding [ 36 ], while concomitant use of aspirin increases the risk of bleeding for both warfarin [ 37 ] and DOACs [ 38 ]. The difference in concomitant medication usage between our cohort and the trial population may explain some of the observed differences in treatment effects.

A key limitation of our study was the inability to match ARISOTLE on ethnicity, meaning the CPRD Aurum cohort included a low number of patients from Asian and Hispanic groups when compared with the RCT (14.5% of participants in ARISTOTLE were Asian compared to 2.4% in our ARISTOTLE-analogous CPRD cohort). There are known racial differences in the treatment effects of OACs with Asian patients experiencing a higher risk of haemorrhagic stroke and intracranial haemorrhage compared with white patients; in ARISTOTLE, Asian participants experienced double the risk of stroke or SE when on warfarin therapy when compared with white participants [ 39 ]. The reasons for the increased risk of bleeding associated with warfarin therapy in Asian patients is hypothesised to be associated with differences in drug metabolism and prevelance of cerebral microbleeds [ 40 ]. The difference in proportion of Asian patients between our cohort and ARISTOTLE is therefore likely to explain some of the differences in treatment effects seen and limits the generalisability of our study, with the results of our study of most relevanance to white patients. This limitation on ethnicity arose from the data source used and time period studied (patients with AF in CPRD Aurum 2013–2019), which had a low proportion of Asian patients, likely due to AF being associated with older age combined with a lower prevalence of AF in Asian patients compared with white patients [ 41 ]. While CPRD Aurum is largely representative of the UK population in relation to ethnicity [ 42 ], diversity is still limited for older individuals. Despite this, CPRD Aurum has shown to be a useful resource for investigating treatment effects in different ethnic groups for indications such as hypertension, which is more prevalent and occurs at a younger age in ethnic minority groups, with similar trial replication methods used to compare antihypertensive treatment effects in underrepresented ethnic groups [ 13 ].

The approach our study used for handling missing data on baseline covariates relied on assumptions on the relationship between missingness, treatment, and outcomes, which may not be valid; however, the low proportion of missing data means that this is unlikely to have impacted the results. In the coarsened exact matching step, the choice of variables will have an impact on the resulting cohort selected, meaning a different combination of variables could lead to different results. There is a risk that residual confounding may be present despite the use of PSM. The use of PSM also has the potential to introduce bias by dropping patients from the cohort [ 19 ]; however, PSM is well suited to the process of trial emulation including prevalent users, and a low number of apixaban users were dropped due to unsuccessful matching. The inclusion of prevalent users of warfarin in the cohort risks the introduction of selection bias [ 20 , 21 ]; this was avoided by use of a method shown to produce unbiased estimates in a simulation study [ 21 ]. We found consistent results between our new and prevalent user strata across multiple outcomes providing reassurance the method used was likely to have successfully avoided selection bias.

Apixaban along with other DOACs were rapidly adopted as preferred first-line OAC in AF during the study period; it was therefore not possible to match on calendar date leading to a difference in follow-up time between the treatment arms in our cohort. A higher proportion of warfarin users switched to alternative OAC during follow-up compared with those prescribed apixaban (16% versus 6%). The impact of this differential switching during follow-up was addressed in the sensitivity analyses. The availability of new alternative treatments during the study period also means there is a risk of channelling bias in that over time the patients still on warfarin are more likely to be those doing well on warfarin. INR control prior to the index date was not included in the PS for the prevalent users due to a high rate of missing data; however, other variables associated with poor INR control were included in the models, and an exploratory post hoc analysis including a variable for poor INR control gave results consistent with the primary results.

Adherence to treatment was difficult to assess in our study due to automatic repeat prescriptions; treatment persistence was more useful in providing a measure of pattern of medicine use over time. In the analysis by TTR, the adherence of patients using apixaban was not accounted for; however, a previous UK study showed apixaban had higher adherence than VKAs [ 43 ], meaning we would expect to see better effectiveness outcomes in apixaban. Futhermore, the use of IPTW in the analysis by TTR means predictors of poor adherence are likely to have been balanced between treatments. The analysis of TTR is limited by this being a post-baseline measure available for only 1 treatment arm leading to a risk of selection bias in this analysis—patients with TTR available in the study may be more healthy than those without this measure given that patients have to survive and not be hospitalised to have INR measurements available in CPRD Aurum. The limitation of use of a post-baseline measurement available for 1 treatment arm was also evident in the RCTs of DOACs versus warfarin and is mitigated in our study through the use of IPTW and predicted TTR for patients that were missing TTR (using a model to predict TTR that used INR measurements restricted to the first year of follow-up). Given the risk of selection bias in the analysis by TTR and risk of misclassification of TTR for those missing TTR, these results should be considered exploratory and interpreted with caution. Sensitivity analyses in our cohort using an on-treatment censoring scheme showed evidence of attrition bias. The regular measurement of INR and availability of alternative anticoagulants makes warfarin therapy particularly prone to attrition bias since a patient may be more likely to switch to a DOAC if their INR is frequently out of the optimal range or if they have not been adhering to scheduled INR testing.

To conclude, we found that applying a reference trial emulation approach allowed us to emulate a landmark randomised trial of apixaban versus warfarin using UK noninterventional data, with results meeting prespecified benchmarking criteria based on the reference trial results. This trial emulation method provides valid treatment effect estimates for apixaban compared to warfarin and can be used to determine risks and benefits of AF medications in people treated in routine clinical care. This study demonstrates a successful real-world application of novel methods that have been proposed for the inclusion of prevalent users in observational studies, with the application of an adaptation to mimic the screening process making the method suitable for emulation of RCTs that include prevalent users. These methods could be adapted for emulation of RCTs in other therapeutic areas and for looking at patient groups underrepresented or excluded from RCTs.

The weaker overall treatment benefit observed in our cohort appears to be due to a higher proportion of patients with well-controlled warfarin in the UK clinical context, compared with the trial. Our exploratory analysis by TTR showed similar results for stroke and a greater benefit for apixaban for major bleeding compared with TTR <0.75; conversely, a slightly higher risk of death was observed on apixaban compared with well-controlled warfarin.

The views expressed in this paper are those of the author and not do not necessarily reflect those of the SFDA or its stakeholders. Guaranteeing the accuracy and the validity of the data is a sole responsibility of the research team.

Supporting information

S1 strobe checklist, s1 isac protocol, s1 appendix.

Table A1. ARISTOTLE inclusion and exclusion criteria applied to CPRD Aurum. Table A2. Efficacy outcomes results from ARISTOTLE. Table A3. Effectiveness outcomes results in the CPRD Aurum ARISTOTLE-analogous cohort. Table A4. Bleeding outcomes and net clinical outcomes results from ARISTOTLE RCT. Table A5. Bleeding outcomes and net clinical outcomes results in the CPRD Aurum ARISTOTLE-analogous cohort. Table A6. Effectiveness outcomes results in the CPRD Aurum ARISTOTLE-analogous cohort using the on-treatment censoring scheme. Table A7. Treatment status of apixaban and warfarin users in CPRD Aurum ARISTOTLE-analogous cohort during 2.5 years of follow-up. Table A8. Characteristics of apixaban and warfarin users in CPRD Aurum ARISTOTLE-analogous cohort by treatment persistence during 2.5 years of follow-up. Table A9. Effectiveness outcomes results in the CPRD Aurum ARISTOTLE-analogous cohort using later study start date (1 January 2014). Table A10. Summary of noninterventional studies comparing apixaban and warfarin in AF patients.

Abbreviations

Funding Statement

This work was supported by the Medical Research Council (grant number MR/N013638/1 to EMP). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

Data Availability

• PLoS Med. 2024 Aug; 21(8): e1004377.

Decision Letter 0

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Decision Letter 1

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COMMENTS FROM THE ACADEMIC EDITOR

To be able to use routine clinical data from an unselected population in a way that methodologically correctly simulates a randomized trial is very important and useful whenever a new treatment is introduced through industry-sponsored trials only. Actually, even when the trial is performed independently, the issue of a selected population still remains, and results from such an analysis in routinely collected data will still be very worthwhile regarding generalizability.

This paper therefore has a double message that is worthwhile from both respects: the clinical message that in fact warfarin is not inferior to apixaban if the warfarin treatment is good; and the scientific message that it would be good to perform such studies whenever new treatments are being studied.

Having said that, there is maybe one limitation that is not addressed in detail, which is the issue of residual confounding. Even properly performed propensity scores cannot take away unmeasured confounding. The fact that a strong effect is found for death (HR 0.84) for the subjects with TTR in the low range suggests in my opinion that some confounding may still be present, as low TTR is generally associated with worse health and more comorbidity. Also the fact that the effect estimates flip so clearly from below to above one suggests this phenomenon. But even if residual confounding would still be present, I don’t think that would interfere with the conclusion.

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COMMENTS FROM THE REVIEWERS:

Reviewer #1: 1. Thank your your hard work. It's well-written and well-cited report. However, I am not convinced that these analyses add anything new. The subanalysis of "special" groups e.g. patients with cancer, obesity etc. may be more interesting as data are limited.

2. There are known racial differences in the treatment effect of OACs. In your study, 95.7% of patients were White, but in the Aristotle 14.4% of patients were Asians. My concern is the generalizability of the study; and it is worth to discuss as a study limitation.

3. Do you have the data on Apixaban doses? Were they well-adjusted. It is also worth mentioning the higher number of patients with CKD (comparing to the Aristotle), which may affect dosing.

Reviewer #2: Alex McConnachie, Statistical Review

The paper by Powell and colleagues uses CPRD data to perform propensity score matched analyses designed to replicate the ARISTOTLE trial of apixaban vs. warfarin for the treatment of AF. This review looks at their use of statistics.

This is an expertly designed and delivered analysis. The construction of the study cohort is very cleverly done, using various steps to ensure comparability, first to the ARISTOTLE population (where possible) and then between exposed and unexposed individuals. The analysis methods themselves are all good. The Cox models use robust standard errors to account for the matched design, and are appropriately checked for proportional hazards. Sensitivity analyses are an on-treatment analysis and an analysis using a later start date.

Subgroup analyses are done by TTR. Is this just for the patients who switched from warfarin to apixaban, with TTR relating to the period prior to the index date? I note that TTR is not included in Table 2. Also, TTR does not appear to be included in Table 1, as one of the covariates used in the PS matching procedure - should it be? If channelling is a risk, then surely patients with worse TTR might be more likely to be switched to apixaban?

Another possibility is that the subgroup analysis is performed in relation to the TTR of the warfarin users after the index date. After multiple reads of the paper, I believe this may be what was done. Is it appropriate to stratify by a post-baseline characteristic?

For any subgroup analysis I would normally ask to see an interaction test p-value, but that may not be appropriate here (or necessary, given the magnitude of the difference in treatment effect estimates).

The wording of the main conclusion in the abstract did not seem to match the results on first reading. Yes, the results showed non-inferiority, as did ARISTOTLE, but clearly not superiority, which ARISTOTLE did. To say the results are comparable therefore seems incongruous. To describe the treatment effect observed as "weaker" doesn't seem to fit. Looking at the effect estimates and CIs, I would describe the results as showing no treatment effect in the full population. The observation that this is a combination of a treatment effect benefit in the TTR<0.75 group and a treatment harm in the TTR>=0.75 group then makes sense.

Finally, and I don't know enough about the theory to be definitive on this, but I have read that propensity score matching can introduce bias rather than remove it. What assurances can the authors give that the way they have implemented PSM is good? Does it come down to the choice of caliper width?

Reviewer #3: Summary

The authors examined the impact of warfarin time in therapeutic range on outcomes using ARISTOTLE-analogous cohort in the UK. The research concepts are intriguing, the study findings appear highly significant, and the study was well-written.

Here are some comments for revision to improve the manuscript:

1. Introduction: It is recommended to provide a more detailed explanation of how the results would remain consistent or similar to RCT results, even when the population that was excluded from or underrepresented in trials is included. In this regard, the 'validation of results against ARISTOTLE' section in the Methods section may need further elaboration for the benefit of readers.

2. Methods: For the definition of a new user of warfarin or a warfarin-naïve apixaban user, is there a required washout period to ensure their non-use of warfarin for a certain duration?

3. Methods: Why was a caliper of 0.2 chosen for use?

4. Results: 354 apixaban patients who had no matches were mentioned, along with 8846 patients who remained after matching. The numbers do not align (9120 - 354 = 8766).

5. Discussion: In an RCT, participants are expected to maintain good adherence to their assigned treatment. However, in this study, I couldn't find a clear operational definition or justification for 'persistent patients' (e.g., checks at every 6-month time point would suffice?), 'discontinuation' (e.g., a definition using the number of days between prescriptions?), and 'switching' (e.g., when a prescription for a switching drug occurred during or certain days after the index treatment's prescription, how should this be considered?). It would be beneficial to provide further elaboration regarding these in both the Methods and Discussion sections.

6. Discussion: Is emulating an RCT in 2014 still relevant for today's real-world patient populations, given the changing preferences of patients and physicians, as well as evolving clinical practices, guidelines, and recommendations?

7. Discussion: Could we explore future analyses with an extended follow-up period stemming from this study, particularly for the purpose of projecting long-term outcomes from an RCT? Are there any other valuable directions or extensions for this study that we should consider?

Any attachments provided with reviews can be seen via the following link:

Author response to Decision Letter 1

Submitted filename: Responses_to_review.docx

Decision Letter 2

Thank you very much for re-submitting your manuscript "Comparison of oral anticoagulants for stroke prevention in atrial fibrillation: a cohort study in the UK Clinical Practice Research Datalink with emulation of a reference trial (ARISTOTLE)" (PMEDICINE-D-23-02702R2) for review by PLOS Medicine.

I have discussed the paper with my colleagues and it was also seen again by the academic editor and the statistical reviewer. I am pleased to say that provided the remaining editorial and production issues are dealt with we are planning to accept the paper for publication in the journal.

The remaining issues that need to be addressed are listed at the end of this email. Any accompanying reviewer attachments can be seen via the link below. Please take these into account before resubmitting your manuscript:

In revising the manuscript for further consideration here, please ensure you address the specific points made by each reviewer and the editors. In your rebuttal letter you should indicate your response to the reviewers' and editors' comments and the changes you have made in the manuscript. Please submit a clean version of the paper as the main article file. A version with changes marked must also be uploaded as a marked up manuscript file.

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If you have any questions in the meantime, please contact me or the journal staff on gro.solp@enicidemsolp .  

We look forward to receiving the revised manuscript by Mar 15 2024 11:59PM.   

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Requests from Editors:

Thank you for your detailed and considered responses to previous editor and reviewer comments. Please see below for further comments which we require that you address prior to publication.

Suggest emphasizing more clearly the fact that this is target trial emulation study. Perhaps,

“Comparison of oral anticoagulants for stroke prevention in atrial fibrillation using the UK Clinical Practice Research Datalink Aurum: A reference trial (ARISTOTLE) emulation study”.

Abstract Background:

We appreciate the inclusion of additional detail which is very helpful to ascertain the aim of your study. For the purpose of brevity suggest removing lines 25-27 from the abstract and restricting to the introduction of main manuscript. Suggesting including a final sentence in the 1st paragraph of ‘Background’ to read as follows:

‘Reference trial emulation allows evidence to be generated around treatment effects in groups excluded or underrepresented in the original trials.’

Abstract Methods & Findings:

Line 37 – suggest revising ‘warfarin CPRD users’ to ‘warfarin users in the CPRD Aurum’.

Abstract Conclusions:

Do these data tell us anything about the usefulness of this methodological approach to investigate treatment effects for other conditions?

Line 65 – suggest, ‘This study used routinely collected health data from the UK to…’

Lines 69-70 – suggest, ‘…help to understand how transferrable RCT results are to ‘real-world’ practices and whether this methodological approach can help to improve treatment options and outcomes for patient groups currently underrepresented in clinical trials.’ Or similar.

Line 75 – suggest, ‘UK primary care data’.

Line 81 – sentence beginning ‘This may be explained…’ suggest removing and (after paraphrasing) suggest placing as part of the final bullet point of the ‘What do these findings mean?’ sub-section as a limitation.

Lines 88 and 90 – suggest swapping these 2 bullet points around such that the ‘benefits’ of the methodological approach are listed sequentially.

Line 93 – suggest removing the word ‘these’ as this methodology could be applied to various treatment strategies for a number of different conditions – this would be worth emphasizing as it is a major selling point of your study, at least in my opinion! Might also be worth giving an example and making a clear distinction between those that are excluded from clinical trials (those with multimorbidity, for example) and those who are underrepresented (certain ethnic minority groups, for example).

Line 96 – please revise the final point in line with previous comments (see line 81).

INTRODUCTION

As noted above, the methodological approach is a really big selling point which deserves emphasis but not only for anticoag. in AF, also for a variety of treatments and differing conditions.

As above, might be worth differentiating & defining the excluded and underrepresented groups so that readers can make tangible associations, which should increase the impact of your take-home message.

Line 140 – would ‘influenced by’ be more accurate than ‘dependent upon’?

TABLES and FIGURES

Table 3 – for the purpose of formatting requirements, please include a leading zero for all numerical values in the standardized difference column, for example, row 3 should read ‘0.008’. If not for the purpose of transparent reporting, please clearly explain the reasons why not.

Some parts of your discussion read very well and others are less nuanced and focused. Suggest revising for improved nuance and clarity. The strengths and limitations of your findings in context of your chosen methodological approach, which we think has clear strengths and transferability as well as some limitations, could be more clearly presented in parts.

Please remove all sub-headings such that the discussion reads as continuous prose.

Lines 528-530 – when referring to ‘prevalent users’ do you mean users of warfarin, apixaban or both. Please amend for clarity.

Line 568 onwards – you discuss here the implications of ethnicity on your results compared to ARISTOTLE. For further clarity, could you elaborate on the reasons why such a difference was observed. Was this a consequence of the database or an effect of PSM? Considering that this (methodological) approach could help in ascertaining treatment effects in those who are underrepresented in trials (such as ethnic minority groups), what implications might this finding have on the usefulness of either the dataset or the methodological approach more broadly?

Please ensure that abbreviations are defined throughout the supporting information, including tables and figures as relevant.

Thank you for including the published protocol. Apologies for the confusion at the time of our previous request we were asking for the original protocol document (i.e., as used for your study approval process or data access process) not the BMJ published protocol article, this does not need to be included, the reference will suffice. Please amend.

SOCIAL MEDIA

To help us extend the reach of your research, please detail any X (formerly Twitter) handles you wish to be included when we tweet this paper (including your own, your coauthors’, your institution, funder, or lab) in the manuscript submission form when you re-submit the manuscript.

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Comments from Reviewers:

I thank the authors for their consideration of my original comments. I am happy with their responses, and have no further comments to make.

Author response to Decision Letter 2

28 Mar 2024

Submitted filename: Responses_to_review_15Mar2024.docx

Decision Letter 3

23 May 2024

Thank you very much for re-submitting your manuscript "Comparison of oral anticoagulants for stroke prevention in atrial fibrillation using the UK Clinical Practice Research Datalink Aurum: A reference trial (ARISTOTLE) emulation study" (PMEDICINE-D-23-02702R3) for review by PLOS Medicine.

As discussed via email please re-submit your manuscript once the required revisions to the analyses are complete.

We look forward to receiving the revised manuscript by 6th June but if you require more time then please let me know. 

Kind regards

Philippa Dodd, MBBS MRCP PhD 

Author response to Decision Letter 3

30 May 2024

Submitted filename: Responses_to_review_30May2024.docx

Decision Letter 4

12 Jun 2024

Dear Dr Powell, 

On behalf of my colleagues and the Academic Editor, Professor Suzanne Cannegieter, I am pleased to inform you that we have agreed to publish your manuscript "Comparison of oral anticoagulants for stroke prevention in atrial fibrillation using the UK Clinical Practice Research Datalink Aurum: A reference trial (ARISTOTLE) emulation study" (PMEDICINE-D-23-02702R4) in PLOS Medicine.

Before your manuscript can be formally accepted you will need to complete some formatting changes, which you will receive in a follow up email. Please be aware that it may take several days for you to receive this email; during this time no action is required by you. Once you have received these formatting requests, please note that your manuscript will not be scheduled for publication until you have made the required changes.

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We also ask that you take this opportunity to read our Embargo Policy regarding the discussion, promotion and media coverage of work that is yet to be published by PLOS. As your manuscript is not yet published, it is bound by the conditions of our Embargo Policy. Please be aware that this policy is in place both to ensure that any press coverage of your article is fully substantiated and to provide a direct link between such coverage and the published work. For full details of our Embargo Policy, please visit http://www.plos.org/about/media-inquiries/embargo-policy/ .

Thank you again for submitting to PLOS Medicine. We look forward to publishing your paper. 

Pippa 

Senior Editor 

Guidance for Pre- and Post-Construction Monitoring to Detect Changes in Marine Bird Distributions and Habitat Use Related to Offshore Wind Development

As the offshore wind (OSW) industry develops in the U.S. Atlantic, effective monitoring is needed to detect potential effects to wildlife. A Specialist Committee was convened by New York’s Offshore Wind Environmental Technical Working Group (E-TWG) and chaired by the U.S. Fish and Wildlife Service with the goal of advancing recommendations for the effective detection and characterization of changes in the distributions and habitat use of marine birds in relation to OSW energy development.

The committee’s recommendations are specifically focused on:

• Marine birds and OSW development in the U.S. Atlantic, though many of the recommendations are broadly relevant to other geographies.
• Studies of changes in marine bird movement behavior, distributions, and habitat use, namely displacement, attraction, and macro-to meso-scale avoidance.
• Studies intended to detect effects from OSW development, not assess risk or characterize avian resources prior to construction.
• Informing project-specific monitoring, although many recommendations are also applicable to studies at larger scales.

While there are various potential effects from OSW development on marine birds, and all deserve dedicated research recommendations, understanding displacement-related effects is a key research priority. The deliberative process used to develop these recommendations brought together experts to reach consensus on the best available science to conduct studies of marine birds at OSW facilities. This Specialist Committee firmly recommends that:

• Statistically robust monitoring should be conducted at all OSW lease areas to detect and characterize changes in distributions and habitat use of marine birds, and
• This guidance form the basis for federal guidelines focused on how to conduct pre-and post-construction monitoring at individual OSW facilities in the U.S. Atlantic.

The guidance includes:

• General study design recommendations for all types of displacement, avoidance, and attraction studies;
• Recommendations for conducting observational surveys, a key method for displacement studies; and
• Recommendations for future guidance and research.

Guidance Document Summary

Guidance Document

Contents Part I. Summary      S.1 General Recommendations      S.2 Detailed Recommendations for Observational Surveys      S.3 Future Directions Part II. Introduction      1.0 Background and Purpose           1.1 Terminology      2.0 Rationale      3.0 Focus of Guidance Part III. General Study Design Recommendations      4.0 Key Research Questions           4.1 Key Research Questions to Examine Displacement, Attraction, and Avoidance           4.2 Using Site-Specific Data to Inform Regional-Scale Questions      5.0 Identifying Focal Taxa           5.1 Understanding Exposure           5.2 Understanding Sensitivity and Uncertainty           5.3. Additional Considerations for Selection of Focal Taxa      6.0 Choosing Appropriate Methodologies           6.1 Selecting Study Methods           6.2 Considerations for Specific Methods           6.3 Summary: Choosing Appropriate Methods      7.0 Developing an Effective Study Design           7.1 Study Objectives           7.2 Study Design           7.3 Data Sharing and Coordination      8.0 Data Consistency and Transparency Recommendations Part IV. Recommendations for Boat-based and Aerial Surveys      9.0 Connection Between Site Assessment Surveys and Pre-Construction Surveys to Detect Effects      10.0 Survey Design and Methodology Recommendations           10.1 Define Clear Study Goals           10.2 Use of Gradient Study Design           10.3 Assessment of Spatial and Temporal Coverage           10.4 Data Collection Methods           10.5 Review of Data           10.6 Data Analysis           10.7 Data Reporting Part V. Recommendations for Future Guidance and Research      11.0 Next Steps for Guidance      12.0 Additional Guidance, Frameworks, and Research Needs Part VI. Literature Cited Part VII. Appendices      Appendix A. Guidance Development Methods      Appendix B. Glossary of Key Terminology      Appendix C. Literature Review: Macro- to Meso-Scale Changes in Marine Bird Distributions and Habitat Use      Appendix D. Assessment Rubric for Study Plans