abstract for literature review example

The abstract is characterized by the use of the past tense, the third person, passive, and the non-use of negatives…. It is written in tightly worded sentences, which avoid repetition, meaningless expressions, superlatives, adjectives, illustrations, preliminaries, descriptive details, examples, footnotes. In short it eliminates the redundancy which the skilled reader counts on finding in written language and which usually facilitates comprehension. [ 12 ]

In systematic reviews, it is easy to find sentences like “Trial eligibility and quality were assessed” that would be more readable if they were written as “We assessed the eligibility and the quality of the trials.” Furthermore, there are often short telegrammatic communications, some of which contain no verbs. Figure 1 provides an example (under the subheading “Selection criteria”).

There are, of course, numerous guidelines on how to write clear abstracts and more readable medical text [ 13–16 ] but, at present, there are few such guidelines for writing the abstracts of systematic reviews. Mulrow, Thacker, and Pugh [ 17 ] provide an excellent early example, and there are now regularly updated guidelines in the Cochrane Handbook [ 18 ].

Nonetheless, even when such guidelines are followed, evaluating the clarity of medical text is not easy. But some methods of doing so may be adapted from the more traditional literature on text evaluation. Schriver, for example, describes three different methods of text evaluation—text-based, expert-based, and reader-based methods [ 19 ]:

Although all three methods of evaluation are useful, especially in combination, this writer particularly recommends reader-based methods for evaluating the readability of abstracts in systematic reviews. This recommendation is because the readers of such systematic reviews are likely to be quite disparate in their aims, needs, and even in the languages that they speak. As the 1999 Cochrane Handbook put it:

Abstracts should be made as readable as possible without compromising scientific integrity. They should primarily be targeted to health care decision makers (clinicians, consumers, and policy makers) rather than just researchers. Terminology should be reasonably comprehensible to a general rather than a specialist medical audience [emphasis added]. [ 20 ]

Expert-based measures on their own may be misleading. For instance, there is evidence to suggest that the concerns of professionals are different from those of other personnel [ 21 ]. Wilson et al. [ 22 ], for instance, report wide differences between the responses of general practitioners (GPs) and patients in the United Kingdom in responses to questions concerning the content and usefulness of several patient information leaflets. Table 3 shows some of their replies.

Table 3 Differences between general practitioners (GPs) and patients in their views about particular patient information leaflets

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THE STRUCTURE OF THE TEXT

In recent times, particularly in the medical field, there has been great interest in the use of so-called “structured abstracts”—abstracts that typically contain subheadings, such as “background,” “aims,” “methods,” “results,” and “conclusions.” Indeed, the early rise in the use of such abstracts was phenomenal [ 23 ], and it has no doubt continued to be so up to the present day. Evaluation studies have shown that structured abstracts are more effective than traditional ones, particularly in the sense that they contain more information [ 24–31 ]. However, a caveat here is that some authors still omit important information, and some still include information in the abstract that does not match exactly what is said in the article [ 32–35 ].

Additional research has shown that structured abstracts are sometimes easier to read and to search than are traditional ones [ 36, 37 ], but others have questioned this conclusion [ 38, 39 ]. Nonetheless, in general, both authors and readers apparently prefer structured to traditional abstracts [ 40–42 ]. The main features of structured abstracts that lead to these findings are that:

Nonetheless, there are some difficulties—and these difficulties become more apparent after considering the structured abstracts of systematic reviews. First of all, the typographic practice of denoting the subheadings varies from journal to journal [ 43, 44 ]. Second, and of more relevance here, there is a range of subheadings used both within and among journals [ 45, 46 ], which militates against rapid retrieval. Table 4 shows an example of these variations by listing the subheadings used in the abstracts in just one volume of the Journal of the American Medical Association. Finally, it appears that some authors omit important subheadings or present them in a different order (e.g., reporting the conclusions before the results) [ 47 ].

Table 4 Different numbers of subheadings used in abstracts in the same volume of the Journal of the American Medical Association

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The implications of these difficulties are that a decision needs to be made, based upon appropriate evaluation studies, about what are the key subheadings that can be used consistently in systematic reviews. The journal Evidence-Based Medicine, for example, uses the following six subheadings: “Question(s),” “Data sources,” “Study selection,” “Data extraction,” “Main results,” and “Conclusions,” but the Cochrane Handbook [ 48 ] recommends another seven: “Background,” “Objectives,” “Search strategy,” “Selection criteria,” “Data collection and analysis,” “Main results,” and “Reviewers' conclusions.” Presumably, these different sets of subheadings have developed over time with experience. For example, “Objective(s)” initially preceded “Question(s)” in Evidence-Based Medicine. In the future, refining these subheadings further may be possible by using appropriate typographic cueing, to separate important from minor subheadings, such as those headings used in the Journal of the American Medical Association. It will be essential, however, to use consistent terminology throughout the literature to aid both the creation of and retrieval from the abstracts of systematic reviews. Editors may consult their readers and their authors for possible solutions to this problem.

THE TYPOGRAPHIC SETTING FOR ABSTRACTS OF SYSTEMATIC REVIEWS

Early research on the typographic setting of structured abstracts in scientific articles suggests that the subheadings should be printed in bold capital letters with a line space above each subheading [ 49 ]. But this research has been done with structured abstracts that only have four subheadings. However, the abstracts of systematic reviews are likely to have more than four-subheadings—indeed, as noted above, six or seven seem typical. Also, some of these subheadings may be more important than others.

Generally speaking, there are two ways of clarifying the structure in typography. One is to vary the typography, the other to vary the spacing [ 50, 51 ]. In terms of typography, not overdoing is best; there is no need to use two cues when one will do. Thus, it may be appropriate to use bold lettering for the main subheadings and italic lettering for the less important ones, without adding the additional cues of capital letters or underlining. Also, as the subheadings appear as the first word on a line, placing a line space above them enhances their effectiveness, so there is no need to indent the subheadings as well. The abstracts published in the Cochrane Library follow this procedure.

Finally in this section, it should be noted that it is easier to read an abstract:

CONCLUSIONS

The research reviewed above suggests that, in presenting the abstracts to systematic reviews, attention needs to be paid to their language, their structure, and their typographic design. Figure 1 shows a “before and after” example for a fictitious abstract for a systematic review. The purpose of this example is to encapsulate the argument of this paper and to show how changes in wording and typography can enhance the clarity of an abstract for a systematic review.

Acknowledgments

The author is indebted to Iain Chalmers, Philippa Middleton, Mark Starr, and anonymous referees for assistance in the preparation of this paper.

* Based on invited presentation at the VIIth Cochrane Colloquium, Rome, Italy, October 1999.

11.8 Writing an abstract

All full reviews must include an abstract of not more than 400 words. The abstract should be kept as brief as possible without sacrificing important content. Abstracts to Cochrane reviews are published in MEDLINE and the Science Citation Index, and are made freely available on the internet. It is therefore important that they can be read as stand-alone documents.

The abstract should summarize the key methods, results and conclusions of the review and should not contain any information that is not in the review. Links to other parts of the review (such as references, studies, tables and figures) may not be included in the abstract. A hypothetical example of an abstract is included in Box 11.8.a .

Abstracts should be targeted primarily at healthcare decision makers (clinicians, informed consumers and policy makers) rather than just to researchers. Terminology should be reasonably comprehensible to a general rather than a specialist healthcare audience. Abbreviations should be avoided, except where they are widely understood (for example, HIV). Where essential, other abbreviations should be spelt out (with the abbreviations in brackets) on first use. Names of drugs and interventions that can be understood internationally should be used wherever possible. Trade names should not be used.

The content under each heading in the abstract should be as follows:

Background: This should be one or two sentences to explain the context or elaborate on the purpose and rationale of the review. If this version of the review is an update of an earlier one, it is helpful to include a sentence such as “This is an update of a Cochrane review first published in YEAR, and previously updated in YEAR”.

Objectives: This should be a precise statement of the primary objective of the review, ideally in a single sentence, matching the Objectives in the main text of the review. Where possible the style should be of the form “To assess the effects of [intervention or comparison] for [health problem] for/in [types of people, disease or problem and setting if specified]”.

Search methods: This should list the sources and the dates of the last search, for each source, using the active form ‘We searched….’ or, if there is only one author, the passive form can be used, for example, ‘Database X, Y, Z were searched’. Search terms should not be listed here. If the CRG’s Specialized Register was used, this should be listed first in the form ‘Cochrane X Group Specialized Register’. The order for listing other databases should be the Cochrane Central Register of Controlled Trials, MEDLINE, EMBASE, other databases. The date range of the search for each database should be given. For the Cochrane Central Register of Controlled Trials this should be in the form ‘Cochrane Central Register of Controlled Trials ( The Cochrane Library 2007, Issue 1)’. For most other databases, such as MEDLINE, it should be in the form ‘MEDLINE (January 1966 to December 2006)’. Searching of bibliographies for relevant citations can be covered in a generic phrase ‘reference lists of articles’. If there were any constraints based on language or publication status, these should be listed. If individuals or organizations were contacted to locate studies this should be noted and it is preferable to use ‘We contacted pharmaceutical companies’ rather than a listing of all the pharmaceutical companies contacted. If journals were specifically handsearched for the review, this should be noted but handsearching to help build the Specialized Register of the CRG should not be listed.

Selection criteria: These should be given as ‘ [type of study] of [type of intervention or comparison] in [disease, problem or type of people]‘ . Outcomes should only be listed here if the review was restricted to specific outcomes.

Data collection and analysis: This should be restricted to how data were extracted and assessed, and not include details of what data were extracted. This section should cover whether data extraction and assessments of risk of bias were done by more than one person. If the authors contacted investigators to obtain missing information, this should be noted here. What steps, if any, were taken to identify adverse effects should be noted.

Main results: This section should begin with the total number of studies and participants included in the review, and brief details pertinent to the interpretation of the results (for example, the risk of bias in the studies overall or a comment on the comparability of the studies, if appropriate). It should address the primary objective and be restricted to the main qualitative and quantitative results (generally including not more than six key results). The outcomes included should be selected on the basis of which are most likely to help someone making a decision about whether or not to use a particular intervention. Adverse effects should be included if these are covered in the review. If necessary, the number of studies and participants contributing to the separate outcomes should be noted, along with concerns over quality of evidence specific to these outcomes. The results should be expressed narratively as well as quantitatively if the numerical results are not clear or intuitive (such as those from a standardized mean differences analysis). The summary statistics in the abstract should be the same as those selected as the defaults for the review, and should be presented in a standard way, such as ‘odds ratio 2.31 (95% confidence interval 1.13 to 3.45)’. Ideally, risks of events (percentage) or averages (for continuous data) should be reported for both comparison groups. If overall results are not calculated in the review, a qualitative assessment or a description of the range and pattern of the results can be given. However, ‘vote counts’ in which the numbers of ‘positive’ and ‘negative’ studies are reported should be avoided.

Authors’ conclusions: The primary purpose of the review should be to present information, rather than to offer advice or recommendations. The Authors’ conclusions should be succinct and drawn directly from the findings of the review so that they directly and obviously reflect the main results. Assumptions should generally not be made about practice circumstances, values, preferences, tradeoffs; and the giving of advice or recommendations should generally be avoided. Any important limitations of data and analyses should be noted. Important conclusions about the implications for research should be included if these are not obvious.

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How to Write an Abstract | Steps & Examples

Published on February 28, 2019 by Shona McCombes . Revised on November 11, 2022 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 .

Abstract example, when to write an abstract, step 1: introduction, step 2: methods, step 3: results, step 4: discussion, tips for writing an abstract, 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.

You will almost always have to include an abstract when:

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:

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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.

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.

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.

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

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.

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:

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

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.

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

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:

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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The Contents of an Abstract · the context or background information for your research; the general topic under study; the specific topic of your research · the
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An abstract is a complete version or form of your article. It is the entire article epitomized, covering the major points, content and scope of your argument
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The aims, methods, results, and conclusions of systematic reviews need to be presented in a consistent way to help search and retrieval. The typographic
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The abstract should summarize the key methods, results and conclusions of the review and should not contain any information that is not in the review. Links to
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In any case, the abstract for a narrative/literature review for a journal article should start with two lines of background information on
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You can include some brief context on the social or academic relevance of your dissertation topic, but don't go into detailed background