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PRISMA for Abstracts: Reporting Systematic Reviews in Journal and Conference Abstracts

PRISMA for Abstracts: Reporting Systematic Reviews in Journal and Conference Abstracts Guidelines and Guidance PRISMA for Abstracts: Reporting Systematic Reviews in Journal and Conference Abstracts 1 1 2 2,7 3 Elaine M. Beller *, Paul P. Glasziou , Douglas G. Altman , Sally Hopewell , Hilda Bastian , 4 5 6 6 " Iain Chalmers , Peter C. Gøtzsche , Toby Lasserson , David Tovey , for the PRISMA for Abstracts Group 1 Centre for Research in Evidence-Based Practice, Bond University, Gold Coast, Australia, 2 Centre for Statistics in Medicine, University of Oxford, Oxford, United Kingdom, 3 National Center for Biotechnology Information, National Library of Medicine, Washington DC, United States of America, 4 James Lind Initiative, Oxford, United Kingdom, 5 Nordic Cochrane Centre, Copenhagen, Denmark, 6 Cochrane Editorial Unit, London, United Kingdom, 7 INSERM, Paris, France give more complete information, and facilitate the finding of Introduction information by the reader. When readers screen the title of an article, and parts of its Despite the adoption of structured abstracts, studies of the quality abstract, they try to determine whether or not to devote their of abstracts of clinical trials have demonstrated that improvement is scarce time to reading on. Some may be screening literature to needed [8,9], and a study of systematic review abstracts demon- identify the articles that are systematic reviews. Thus, the main strated that the direction of the effect or association could not be function of an abstract of a systematic review should be to signal its determined in one in four abstracts from the general and specialty systematic methodology. For most readers, the findings described medical literature [10]. The PRISMA Statement [11] gives some in the abstract will also be key, either as the sole part of an article guidance for abstracts, closely linked to commonly used headings in that will be read, or to determine whether reading the full text is structured abstracts. After observing that the quality of abstracts of required. Abstracts of systematic reviews are very important, as systematic reviews is still poor [10], we decided to develop an some readers cannot access the full paper, such that abstracts may extension to the PRISMA Statement to provide guidance on writing be the only option for gleaning research results. This can be abstracts for systematic reviews. We also wanted to provide a because of a pay wall, low Internet download capacity, or if the full checklist enabling the items suggested to fit into any set of headings article is only available in a language not understood by the mandated by a journal or conference submission. reader. Readers in countries where English is not the primary language may have access to an abstract translated to their own Methods for Development of the Checklist language, but not to a translated full text. Conversely, a large proportion of systematic reviews are published by health We established a steering committee (EMB, PPG, SH, DGA). In technology agencies in non-English speaking countries [1], many collaboration with the steering group of the PRISMA Statement [11], of which provide only the abstract in English. we used the Statement to inform our selection of potential items for The predominance of the abstract in biomedical literature use is the checklist of essential items that authors should consider when clear. Within queries to PubMed, most readers look only at titles; reporting the primary results of a systematic review in a journal or only half of searches result in any clicks on content [2]. The conference abstract. The committee generated a list of items from average number of titles clicked on to obtain the abstract or full PRISMA and other sources of guidance and information on text, even after retrieving several searches in a row, is less than five. structured abstracts and abstract composition and reporting Of those clicks, abstracts will be represented about 2.5 times more [7,11,12], which were found using a thorough search of the literature. often than full texts of articles [2]. Even people going straight to a In preparation for a consensus meeting, we used a modified PDF or full text are likely to start, and perhaps end, with reading Delphi consensus survey method [13] to select and reduce the the abstract. The frequency of viewing full texts is somewhat higher among people searching the Cochrane Database of Citation: Beller EM, Glasziou PP, Altman DG, Hopewell S, Bastian H, Systematic Reviews [3], but the same pattern is clear. After the et al. (2013) PRISMA for Abstracts: Reporting Systematic Reviews in Journal and title, the abstract is the most read part of a biomedical article. Conference Abstracts. PLoS Med 10(4): e1001419. doi:10.1371/journal.pmed.1001419 Abstracts can be useful for screening by study type [4]; Published April 9, 2013 facilitating quick assessment of validity [4,5]; enabling efficient This is an open-access article, free of all copyright, and may be freely reproduced, perusal of electronic search results [4,6]; clarifying to which distributed, transmitted, modified, built upon, or otherwise used by anyone for any lawful purpose. The work is made available under the Creative Commons CC0 patients and settings the results apply [4,5]; providing readers and public domain dedication. peer reviewers with explicit summaries of results [5]; facilitating Funding: This research was supported (in part) by the Intramural Research the pre-publication peer review process [7]; and increasing Program of the NIH, National Center for Biotechnology Information (National precision of computerised searches [6,7]. Library of Medicine). The funders had no role in study design, data collection and Structured abstracts were introduced in the medical literature analysis, decision to publish, or preparation of the manuscript. about 25 years ago [4–6]. They provide readers with a series of Competing Interests: TL is employed by The Cochrane Collaboration. TL is an headings, generally about the purpose, methods, results, and editor (unpaid) for the Cochrane Airways Group. The authors have declared that no other competing interests exist. conclusions of the report, and have been adopted by many Abbreviations: PICOS, participants, interventions, comparators, outcomes, and journals and conferences. They act as a prompt to the writer to study designs. * E-mail: [email protected] " Membership of the PRISMA for Abstracts Group is provided in the The Guidelines and Guidance section contains advice on conducting and Acknowledgments. reporting medical research. Provenance: Not commissioned; externally peer reviewed. PLOS Medicine | www.plosmedicine.org 1 April 2013 | Volume 10 | Issue 4 | e1001419 Scope of PRISMA for Abstracts Summary Points The PRISMA for Abstracts checklist focuses on truthful The abstract of a systematic review should provide a representation of a systematic review in an abstract. We developed structured summary that enables a quick assessment of the checklist to help authors report all types of systematic reviews, the review’s validity and applicability, and easy identifi- but recognise that the emphasis is on systematic reviews of cation in electronic searching. evaluations of interventions where one or more meta-analyses are Despite published guidance on writing the abstract in conducted. Authors who address questions on aetiology, diagnostic the PRISMA Statement guiding the reporting of system- test accuracy, or prognosis may need to modify items or include atic reviews in general and elsewhere, evaluations show other items in their abstract to reflect the essentials of the full that reporting of systematic reviews in journal and report. conference abstracts is poor. We developed consensus-based reporting guidelines as The PRISMA for Abstracts Checklist an extension to the PRISMA Statement on good reporting of systematic reviews and meta-analyses in The checklist is shown in Table 1. An explanation for each item abstracts. is given below. Citations for the examples of good reporting are in The PRISMA for Abstracts checklist gives authors a Table 2. framework for condensing their systematic review into the essentials for an abstract that will meet the needs of Section 1: TITLE many readers. Item 1: Title. Identify the report as a systematic review, meta- analysis, or both. number of possible checklist items. Each item was rated by survey Examples: 1a. ‘‘Systematic review and meta-analysis of the participants as ‘‘omit’’, ‘‘possible’’, ‘‘desirable’’, or ‘‘essential’’ to diagnostic and therapeutic role of water-soluble contrast agent in include in the final checklist. From the first round of the survey, adhesive small bowel obstruction.’’ the ranked items were divided into three lists for the second round. 1b. ‘‘Inhaled corticosteroids vs placebo for preventing COPD The first list contained the items with the highest rankings, and [chronic obstructive pulmonary disease] exacerbations: a system- participants for the second round were instructed that these would atic review and metaregression of randomized controlled trials.’’ be contained in the checklist unless they received low rankings in Explanation: The abstract should make it clear that the report is the second round. The second list contained the items with a systematic review, meta-analysis, or both (examples 1a and 1b). moderate rankings, and participants were instructed that these Search filters have been developed to identify systematic reviews items were likely to be removed from the checklist unless they [16], but inclusion of the words ‘‘systematic review’’ or ‘‘meta- received high rankings in the second round. The third list analysis’’ in the title may improve indexing and electronic contained the items with low rankings, and participants were searching. instructed that these items would be removed unless they received We also suggest using informative titles that incorporate the very high rankings in the second round. PICOS approach (participants, interventions, comparators, out- For the third round of the Delphi survey, a draft checklist was comes, and study designs). This provides key information about presented, which included only the items ranked highest in rounds the scope of the systematic review. As including all elements of the one and two. The five next highest-ranked items were then PICOS approach may make the title unwieldy, we suggest presented, giving participants an opportunity to choose to include including the most important of these elements in the title. These these in the checklist as well. might be the elements that make this review unusual, or that assist One hundred and forty-seven participants, who were authors of readers in searching for the review. research on abstracts, established authors of systematic reviews, methodologists or statisticians related to systematic reviews, and Section 2: BACKGROUND journal editors, were invited by email to complete the three rounds of the web-based survey. The response rate was 68% (n = 100) for Item 2: Objectives. the first round. Only those who completed round one were invited The research question including components such as to participate in rounds two and three. The response rate for participants, interventions, comparators, and out- round two was 80% (n = 80) and for round three 88% (n = 88). comes. The results of the survey were reported at a two-day consensus- Examples: 2a. ‘‘To assess the effect on survival of supportive style meeting on 13–14 October 2011, in Oxford, United care and chemotherapy versus supportive care alone in advanced NSCLC [non-small cell lung cancer].’’ Kingdom. Fifteen invited experts attended, most of whom had participated in the survey. The meeting began with a review of the 2b. ‘‘To evaluate the risk of serious asthma-related events literature about abstract structure and content, followed by a among patients treated with formoterol.’’ review of the checklist items as proposed by the survey 2c. ‘‘The objective of this study was to investigate the predictive respondents. Meeting participants discussed the items and agreed value of C-reactive protein in critically ill patients.’’ whether they should be included and how each item should be Explanation: Irrespective of the strength and nature of the worded. results reported in the abstract, readers should be able to assess the Following the meeting, the checklist was distributed to the questions that the review intended to address. The objectives in an participants to ensure it reflected the decisions made. This abstract should convey succinctly the broad aims of the systematic explanatory document was drafted and circulated through several review. Objectives should reflect what the review intended to iterations among members of the writing subcommittee who had evaluate, such as benefit (example 2a), harms (example 2b), all participated in the meeting. We developed this document using association, predictive value (example 2c), of the intervention or the template for the PRISMA Statement [11], which in turn was exposure of interest and the population or context in which this is based on the methods of the CONSORT Group [14,15]. being studied. PLOS Medicine | www.plosmedicine.org 2 April 2013 | Volume 10 | Issue 4 | e1001419 Table 1. The PRISMA for Abstracts Checklist. TITLE 1. Title: Identify the report as a systematic review, meta-analysis, or both. BACKGROUND 2. Objectives: The research question including components such as participants, interventions, comparators, and outcomes. METHODS 3. Eligibility criteria: Study and report characteristics used as criteria for inclusion. 4. Information sources: Key databases searched and search dates. 5. Risk of bias: Methods of assessing risk of bias. RESULTS 6. Included studies: Number and type of included studies and participants and relevant characteristics of studies. 7. Synthesis of results: Results for main outcomes (benefits and harms), preferably indicating the number of studies and participants for each. If meta-analysis was done, include summary measures and confidence intervals. 8. Description of the effect: Direction of the effect (i.e., which group is favoured) and size of the effect in terms meaningful to clinicians and patients. DISCUSSION 9. Strengths and Limitations of evidence: Brief summary of strengths and limitations of evidence (e.g., inconsistency, imprecision, indirectness, or risk of bias, other supporting or conflicting evidence). 10. Interpretation: General interpretation of the results and important implications. OTHER 11. Funding: Primary source of funding for the review. 12. Registration: Registration number and registry name. doi:10.1371/journal.pmed.1001419.t001 (example 3d). This is important as inclusion, or not, of studies Section 3: METHODS published in languages other than English (examples 3c and 3d), Item 3: Eligibility criteria. unpublished data, or older data can influence the estimates of Study and report characteristics used as criteria for effect or association in meta-analyses [17,18]. inclusion. Item 4: Information sources. Examples – study characteristics: 3a. ‘‘We included randomised Key databases searched and date of last search. controlled trials testing the combination of long-acting ß - agonists Examples: 4a. ‘‘PubMed, ERIC and Cochrane Reviews in combination with inhaled corticosteroids (ICS) versus the same databases from January 1980 to November 2007 were searched or an increased dose of ICS for a minimum of at least 28 days in for studies…’’ children and adolescents with asthma.’’ 4b. ‘‘We searched MEDLINE, EMBASE, the Cochrane 3b. ‘‘… randomized trials of compression stockings versus no Central Register of Controlled Trials (CENTRAL), other trial stockings in passengers on flights lasting at least four hours. Trials registries and product information sheets through June 2008.’’ in which passengers wore a stocking on one leg but not the other, Explanation: The abstract should briefly indicate how thorough or those comparing stockings and another intervention were also and up-to-date the search was by listing key databases searched, eligible.’’ and the date range (example 4a) or date of last search (example Examples – report characteristics: 3c. ‘‘… studies published in 4b). We recommend that if there are three or fewer databases, list English, French, Spanish, Italian and German between 1966 and them all; otherwise list the three that provided the majority of July, 2008 [were included].’’ included studies. 3d. ‘‘We performed a literature search of trials using Item 5: Risk of bias assessment. MEDLINE (January 1966–December 2001) … we retrieved Methods for assessing risk of bias. English- and non-English-language articles for review… we searched for both published and unpublished trials…’’ Example: 5a. ‘‘Risk of bias was assessed regarding randomisa- Explanation: One of the key features distinguishing a systematic tion, allocation sequence concealment, blinding, incomplete outcome data, selective outcome reporting, and other biases.’’ review from a narrative review is the pre-specification of eligibility criteria for including and excluding studies. A clear description of Explanation: Problems in the design and conduct of individual these allows the readers to assess the applicability of the systematic studies can raise questions about the validity of their findings [19]. review findings [11]. Study eligibility characteristics are likely to For example, reports of randomised trials with inadequate include the study questions (PICOS)—types of participants allocation sequence concealment are more likely to show included in the studies (often based on a common clinical exaggerated treatment effects [20]. And non-blinded assessors of diagnosis), the intervention of prime interest and possibly the subjective outcomes generate substantially biased effect estimates specific comparison intervention, the main outcome(s) being [21,22]. It is therefore an important part of a systematic review to assessed—and acceptable study designs (examples 3a and 3b). assess the validity of individual studies, and the risk that they will Eligibility criteria for reports may also include the language of overestimate the true intervention effect. Authors should describe publication, the publication status (e.g., whether to include any methods they used to assess the risk of bias in the included unpublished materials and abstracts) and the year of publication studies (example 5a). PLOS Medicine | www.plosmedicine.org 3 April 2013 | Volume 10 | Issue 4 | e1001419 Table 2. List of references used as examples. Example Number Citation 1a. Branco BC, Barmparas G, Schuriger B, Inaba K, et al. (2010) Systematic review and meta-analysis of the diagnostic and therapeutic role of water-soluble contrast agent in adhesive small bowel obstruction. British Journal of Surgery 97: 470–478. 1b. Agarwal R, Aggarwal AN, Gupta D, Jindal SK (2010) Inhaled corticosteroids vs placebo for preventing COPD exacerbations: a systematic review and metaregression of randomized controlled trials. Chest 137(2): 318–325. 2a. Non-Small Cell Lung Cancer Collaborative Group (2010) Chemotherapy and supportive care versus supportive care alone for advanced non-small cell lung cancer. Cochrane Database of Systematic Reviews. Issue 5, Art. No. CD007309. DOI:10.1002/14651858.CD007309.pub2. 2b. Kemp J, Armstrong L, Wan Y, Alagappan VKT, Ohlssen D, Pascoe S (2011) Safety of formoterol in adults and children with asthma: a meta- analysis. Annals of Asthma, Allergy and Immunology 107(1): 71–78. 2c. Zhang Z, Ni H (2011) C-reactive protein as a predictor of mortality in critically ill patients: a meta-analysis and systematic review. Anaesthesia and Intensive Care 39(5): 854–861. 3a. Chroinin M, Lasserson TJ, Greenstone I, Ducharme FM (2009) Addition of long-acting beta-agonists to inhaled corticosteroids for chronic asthma in children. Cochrane Database of Systematic Reviews Issue 3. Art. No. CD007949. DOI:10.1002/14651858.CD007949. 3b. Clarke MJ, Hopewell S, Juszczak E, Eisinga A, Kjeldstrøm M (2006) Compression stockings for preventing deep vein thrombosis in airline passengers. Cochrane Database of Systematic Reviews. Issue 2, Art. No. CD004002. DOI:10.1002/14651858.CD004002.pub2. 3c. Steinhart AH, Ewe K, Griffiths AM, Modigliani R, Thomsen OO (2003) Corticosteroids for maintenance of remission in Crohn’s disease. Cochrane Database of Systematic Reviews Issue 4. Art. No. CD000301. DOI:10.1002/14651858.CD000301. 3d. Trinh NH, Hoblyn J, Mohanty S, Yaffe K (2003) Efficacy of cholinesterase inhibitors in the treatment of neuropsychiatric symptoms and functional impairment in Alzheimer disease: a meta-analysis. Journal of the American Medical Association 289(2): 210–216. 4a. Bonuck KA, Freeman K, Henderson J (2009) Growth and growth biomarker changes after adenotonsillectomy: systematic review and meta-analysis. Archives of Disease in Childhood 94: 83–91. DOI:10.1136/adc.2008.141192. 4b. Loke YK, Singh S, Furberg CD (2009) Long-term use of thiazolidinediones and fractures in type 2 diabetes: a meta-analysis. CMAJ 180(1): 32–39. 5a. Cho S-H, Lee H, Ernst E (2010) Acupuncture for pain relief in labour: a systematic review and meta-analysis. BJOG 117: 907–920. 6a. Huss A, Scott P, Stuck AE, Trotter C, Egger M (2009) Efficacy of pneumococcal vaccination in adults: a meta-analysis. CMAJ 180(1): 48–58. 6b. Alexander LD, Gilman DRD, Brown DR, Brown JL, Houghton PE (2010) Exposure to low amounts of ultrasound energy does not improve soft tissue shoulder pathology: a systematic review. Physical Therapy 90(1): 14–25. 7a. Al-Majed NS, McAlister FA, Bakal JA, Ezekowitz JA (2011) Meta-analysis: cardiac resynchronization therapy for patients with less symptomatic heart failure. Annals of Internal Medicine 154: 401–412. 7b. Wilson A, Gallos ID, Plana N, Lissauer D, Khan KS, Zamora J et al (2011) Effectiveness of strategies incorporating training and support of traditional birth attendants on perinatal and maternal mortality: meta-analysis. BMJ 343: d7102. DOI: 10.1136/bmj.d7102 7c. Gillies M, Palmateer N, Hutchinson S, Ahmed S, Taylor A, Goldberg D (2010) The provision of non-needle/syringe drug injecting paraphernalia in the primary prevention of HCV among IDU: a systematic review. BMC Public Health 10: 721. 8a. Jolly SS, Amlani S, Hamon M, Yusuf S, Mehta SR (2009) Radial versus femoral access for coronary angiography or intervention and the impact on major bleeding and ischemic events: a systematic review and meta-analysis of randomized trials. American Heart Journal 157(1): 132–140. 8b. Lam LL, Cameron PA, Schneider HG, Abramson MJ, Muller C, et al. (2010) Meta-analysis: effect of B-type natriuretic peptide testing on clinical outcomes in patients with acute dyspnea in the emergency setting. Annals of Internal Medicine 153(11): 728–735. 8c. Madsen MV, Gøtzsche PC, Hrobjartsson A (2009) Acupuncture treatment for pain: systematic review of randomised clinical trials with acupuncture, placebo acupuncture, and no acupuncture groups. BMJ 338: a3115. DOI:10.1136/bmj.a3115. 9a. Santangeli P, Di Biase L, Dello Russo A, Casella M, Bartoletti S et al (2010) Meta-analysis: age and effectiveness of prophylactic implantable cardioverter-defibrillators. Annals of Internal Medicine 153(9): 592–599. 9b. Ceglia L, Lau J, Pittas AG (2006) Meta-analysis: efficacy and safety of inhaled insulin therapy in adults with diabetes mellitus. Annals of Internal Medicine 145(9): 665–675. 9c. Lin J S, O’Connor E, Whitlock EP, Beil TL (2010) Behavioral counseling to promote physical activity and a healthful diet to prevent cardiovascular disease in adults: a systematic review for the U.S. Preventive Services Task Force. Annals of Internal Medicine 53(11): 736– 9d. Zoungas S, Ninomiya T, Huxley R, Cass A, Jardine M, et al. (2009) Systematic review: sodium bicarbonate treatment regimens for the prevention of contrast-induced nephropathy. Annals of Internal Medicine 151: 631–638. 10a. Chandra D, Parasini E, Mozaffarian D (2009) Meta-analysis: travel and risk for venous thromboembolism. Annals of Internal Medicine 151(3): 180–190. 10b. Thomson H, Thomas S, Sellstrom E, Petticrew M (2009) The health impacts of housing improvement: a systematic review of intervention studies from 1887 to 2007. American Journal of Public Health 99 Suppl 3: S681–S692. 10c. Wells G, Parkash R, Healey JS, Talajic M, Arnold M, Sullivan S, et al. (2011) Cardiac resynchronization therapy: a meta-analysis of randomized controlled trials. CMAJ 183(4): 421–429. DOI:10.1503/cmaj.101685. 11a. Levy G, Hill MJ, Ramirez CI, Correa L, Ryan ME, et al. (2012) The use of follicle flushing during oocyte retrieval in assisted reproductive technologies: a systematic review and meta-analysis. Human Reproduction 27(8): 2373–2379. 11b. McKnight RF, Adida M, Budge K, Stockton S, Goodwin GM, et al. (2012) Lithium toxicity profile: a systematic review and meta-analysis. Lancet 379(9817): 721–728. DOI:10.1016/S0140-6736(11)61516-X. PLOS Medicine | www.plosmedicine.org 4 April 2013 | Volume 10 | Issue 4 | e1001419 Table 2. Cont. Example Number Citation 12a. Timmons BW, Leblanc AG, Carson V, Connor Gorber S, Dillman C, et al. (2012) Systematic review of physical activity and health in the early years (aged 0–4 years). Applied Physiology, Nutrition and Metabolism 37(4): 773–792. 12b. Stradling C, Chen YF, Russell T, Connock M, Thomas GN, et al. (2012) The effects of dietary intervention on HIV dyslipidaemia: a systematic review and meta-analysis. PLoS ONE 7(6):e38121. Epub 2012 Jun 11. doi:10.1371/journal.pmed.1001419.t002 Many tools exist for assessing the overall risk of bias in included of non-N/S [non-needle/syringe] injecting paraphernalia associ- studies, including scales, checklists and individual components ated with use of NSP [needle and syringe exchange programmes] [23]. Most tools are scales in which various components of quality or SIF [safer injection facilities].’’ Explanation: The results for the main outcomes should be given are scored and combined to give a summary score. This approach can be seriously misleading, however, and should be discouraged. in the abstract. If meta-analyses have been done, include for each the summary measure (estimated effect) and confidence interval. If A preferred approach requires authors to specify which individual methodological components they will assess and to provide a the intention had been to perform meta-analysis, but no meta- analysis was done for one or more main outcomes, the reasons description and judgment for each component for each of the should be stated (e.g., heterogeneity too great). studies assessed [19]. For randomised trials, common components The abstract should make clear the protocol-defined, pre- include: appropriate generation of the allocation sequence [24], specified importance of each outcome reported, and should not concealment of the allocation sequence [20], blinding of partic- report only those outcomes that have statistically significant or ipant and health care providers, blinding of outcome assessors clinically important results. [22], assessment of incomplete outcome data [25], and selective Where possible, given space limitations, the number of studies outcome reporting [26]. and participants for each main outcome should be stated, particularly if only a small proportion of the total number of Section 4: RESULTS studies or patients in the systematic review contributed informa- Item 6: Included studies. tion on a particular outcome. Number and type of included studies and partici- If there are no summary measures, some numerical data may pants, and relevant characteristics of studies. still be given (example 7c), although authors should be wary of Examples: 6a. ‘‘We included 22 trials involving 101 507 making this in the form of ‘‘vote counting’’ where the number of participants: 11 trials reported on presumptive pneumococcal ‘‘positive’’ and ‘‘negative’’ studies is given. Vote counting takes no pneumonia, 19 on all-cause pneumonia and 12 on all-cause account of weighting of studies according to the amount of mortality. The current 23-valent vaccine was used in 8 trials.’’ information they contain [27]. 6b. ‘‘Eight studies included in this review (n = 586 patients, Item 8: Description of effect. median PEDro score = 8.0/10) evaluated various parameters, Direction of the effect (i.e., which group is favoured) including the duration of patients’ symptoms (0–12 months), duty and size of the effect in terms meaningful to patients and cycle (20% and 100%), intensity (0.1–2.0 W/cm2), treatment time clinicians. per session (4.5–15.8 minutes), number of treatments (6–39), and Examples: 8a. ‘‘Radial access reduced major bleeding by 73% total energy applied per treatment (181–8,152 J).’’ compared to femoral access (0.05% vs 2.3%, OR 0.27 [95% CI Explanation: The number of studies, number of participants, 0.16, 0.45], P,0.001).’’ and characteristics of the included studies (examples 6a and 6b) 8b. ‘‘Length of hospital and critical care unit stay were both enable readers to gauge the validity and applicability of the modestly reduced in the tested group compared with the control systematic review’s results. These characteristics might include group, with a mean difference of 21.22 day (CI, 22.31 to 20.14 descriptors of the participants (e.g., age, severity of disease), range day) and 20.56 day (CI, 21.06 to 20.05 day), respectively.’’ of interventions used (e.g., dose and frequency of drug adminis- 8c. ‘‘A small difference was found between acupuncture and tration), and measurement of outcomes (e.g., follow-up times). placebo acupuncture: standardised mean difference 20.17 (95% Item 7: Synthesis of results. confidence interval 20.26 to 20.08)… [in favour of acupunc- Results for main outcomes (benefits and harms), ture]…, corresponding to 4 mm (2 mm to 6 mm) on a 100 mm preferably indicating the number of studies and partic- visual analogue scale.’’ ipants for each. If meta-analysis was done, include Explanation: The results should summarise the main outcomes summary measures and confidence intervals. in words and numbers. The wording should indicate the direction Examples: 7a. ‘‘… CRT [cardiac resynchonization therapy] of the effect (e.g., lower, fewer, reduced; greater, more, increased) reduced all-cause mortality (6 trials, 4572 participants; risk ratio and the size of the effect using familiar units such as percentages, [RR], 0.83 [95% CI, 0.72 to 0.96]) and heart failure hospitaliza- days, or kilograms. Example 8a makes clear the size of the effect tions (4 trials, 4349 participants; RR, 0.71 [CI, 0.57 to 0.87]) even for readers who have difficulty interpreting relative risks and without improving functional outcomes or quality of life.’’ confidence intervals. When a percentage is used, the baseline risk 7b. ‘‘Six studies reported on maternal mortality and our meta- should also be shown, which allows the reader to see what the analysis showed a non-significant reduction (three randomised absolute benefit or harm is, and calculate whichever measures they trials, relative risk 0.79, 0.53 to 1.05, P = 0.12; three non- choose (example 8a). Authors should take care to make it clear randomised studies, 0.80, 0.44 to 1.15, P = 0.26).’’ whether the reported measure is an absolute or a relative one (e.g., 7c. ‘‘Eight studies presented adjusted odds ratios, ranging from where percentage is used as the units of measurement). Where 0.3 to 0.9, suggesting a reduced likelihood of self-reported sharing possible, continuous outcome measures should be expressed in PLOS Medicine | www.plosmedicine.org 5 April 2013 | Volume 10 | Issue 4 | e1001419 familiar units (example 8b), particularly when the standardised If there is insufficient evidence from well-conducted studies to mean difference is used (example 8c). answer the review’s question, this should be made clear to the reader. When the results are not statistically significant, authors should distinguish between those where there is insufficient Section 5: DISCUSSION evidence to rule out a difference between treatments (wide Item 9: Strengths and limitations of evidence. confidence interval), and those which have sufficient evidence Brief summary of strength and limitations of evidence that an important difference is unlikely (narrow confidence (e.g., inconsistency, imprecision, indirectness, or risk of interval). bias, other supporting or conflicting evidence). If the conclusions of the review differ substantially from previous Examples: 9a. ‘‘Four potentially eligible trials were not included systematic reviews, then some explanation might also be provided. in the meta-analysis because mortality data by age group were not Reference could be made to known ongoing studies that have the available.’’ potential to change the result of the review. Possible implications 9b. ‘‘All trials were open label, which may introduce bias. Most for policy and practice should be stated. of the trials were of 24 weeks’ duration or less, limiting assessment of long-term safety.’’ 9c. ‘‘Meta-analyses for some outcomes had large statistical Section 6: OTHER heterogeneity or evidence for publication bias. Only 11 trials Item 11: Funding. followed outcomes beyond 12 months.’’ Primary source of funding for the review. 9d. ‘‘Meta-regression showed that small, poor-quality studies Examples: 11a. ‘‘This work was supported, in part, by the that assessed outcomes soon after radiocontrast administration Program in Reproductive and Adult Endocrinology, NICHD, were more likely to suggest benefit (P,0.05 for all).’’ NIH, Bethesda, MD. The authors have no competing interests to Explanation: The abstract should briefly describe the strengths declare.’’ and limitations of the evidence across studies [28]. Limitations 11b. ‘‘Funding: National Institute for Health Research may include: risk of bias common to many or all studies, such as Programme Grant for Applied Research.’’ lack of blinding for subjective outcomes (example 9b) or Explanation: Studies of the relationship between pharmaceuti- unavailability of data (example 9a); inconsistency of effect or cal company funding and results of clinical trials have shown that association, as demonstrated by high heterogeneity (examples 9c sponsored studies are more likely to have outcomes favouring the and 9d); imprecision, e.g., due to few events or small sample sizes; sponsor [29,30]. This is also the case for systematic reviews [31]. indirectness of the evidence, such as the use of an intermediate or Therefore, the abstract should indicate whether the sponsor of the short-term outcome (examples 9b and 9c); and likely publication research or the researchers might have a conflict of interest in bias (example 9c). Potential strengths of the overall body of respect of the findings of the systematic review, for example, as the evidence that might apply for a particular outcome of a systematic manufacturer of the intervention being evaluated (examples 11a review include: a large effect (example 8a); demonstration of a and 11b). The abstract should include the main source of funding dose-response relationship (example 10a, below); and that all for the systematic review, whether from host institutions or from biases would be likely to reduce the effect rather than increase it. external bodies. One or more of these strengths and limitations may apply to each Item 12: Registration. of the outcomes of the systematic review being described in the Registration number and registry name. abstract. Some of this information may be combined with item 6, Examples: 12a. ‘‘PROSPERO registration: CRD42011 above, when describing the included studies, however a summary 001243.’’ of the overall strengths and limitations of the evidence might also 12b. ‘‘PROSPERO 2011:CRD42011001329.’’ be helpful. Explanation: Registration of systematic reviews provides a Item 10: Interpretation. record of reviews that have been initiated, even if they have not General interpretation of the results and important been published. It is therefore a means of alerting researchers to implications. systematic reviews that are in progress, and serves as a public Examples: 10a. ‘‘Travel is associated with a nearly 3-fold higher record of the proposed systematic review. It also helps to detect risk for VTE [venous thromoboembolism], with a dose-response reporting bias by enabling better identification of unpublished relationship of 18% higher risk for each 2-hour increase in travel systematic reviews, and also to compare the methods or outcomes duration.’’ reported in published reviews with those originally proposed in 10b. ‘‘Housing improvements, especially warmth improve- registered protocols [32]. The abstract should record the name of ments, can generate health improvements; there is little evidence the database with which the review is registered, and the of detrimental health impacts. The potential for health benefits registration number. Cochrane reviews are an exception to this may depend on baseline housing conditions and careful targeting requirement, as they are preceded by a peer reviewed protocol of the intervention. Investigation of socioeconomic impacts that is published in the Cochrane Library and can be downloaded associated with housing improvement is needed to investigate from there. the potential for longer-term health impacts.’’ 10c. ‘‘The cumulative evidence is now conclusive that the Discussion addition of cardiac resynchronization to optimal medical therapy or defibrillator therapy significantly reduces mortality among The title of a systematic review is its first signal of its relevance to patients with heart failure.’’ potential readers. Few titles will entice a reader to invest additional time, but when they do, they ordinarily start—and quite often Explanation: Remembering that some readers may struggle with interpreting the statistical results, an overall summary of the end—with the abstract. The first impression is therefore crucial. main effects—positive or negative—should be given (example We strongly recommend the use of structured abstracts for 10a). This could include an indication of what is clear (example reporting systematic reviews, as does the PRISMA Statement [11]. 10c), what important uncertainties remain (example 10b), and We recognise that journals have developed their own set of whether there is ongoing research addressing these. headings that are considered appropriate for reporting systematic PLOS Medicine | www.plosmedicine.org 6 April 2013 | Volume 10 | Issue 4 | e1001419 reviews, and it is not our intention to suggest changes to these We encourage journals and conference organisers to endorse headings, but to recommend what should be reported under them. the use of PRISMA for Abstracts, in a similar way to CONSORT The order of items and the headings are therefore flexible. For for Abstracts [33]. This may be done by modifying their example, the strengths and limitations may be stated at the end of instructions to authors and including a link to the checklist on the Results, under a separate heading, or with the Discussion or their website. It has been demonstrated that the number of Conclusions, depending on journal requirements. It may also be checklist items reported is improved in journals that require possible to combine items from the checklist into one sentence. For checklist completion as part of the submission process [34]. example, limitations may be combined with a description of the Abstracts should not replace full articles in informing decision included studies (i.e., items 6 and 9 from the checklist). making, but for time-pressed readers and those with limited access We have suggested reporting a minimum set of items. We do to full text reports, the abstract must stand alone in presenting a not advocate that abstracts replace full articles in informing clear and truthful account of the research. The PRISMA for decision making, but we recognise that for many time-pressed Abstracts checklist will guide authors in presenting an abstract that readers, or for those with limited access to the full texts of reports, facilitates a quick assessment of review validity, an explicit it is important that abstracts contain as much information as is summary of results, facilitates pre-publication or conference feasible within the word limit of abstracts. Indeed, for readers who selection peer review, and enables efficient perusal of electronic do not understand the language of publication of the article, the search results. translated abstract may have far more relevance than the full-text article. Acknowledgments A checklist is not sufficient to ensure good abstract writing. For example, the abstract should clearly and truthfully reflect the full We dedicate this paper to the memory of Alessandro Liberati who, among many important achievements, was instrumental in the development and report, and not selectively report results that are statistically implementation of the PRISMA Statement, and had many thoughtful significant while not referring to those that were not. Similarly, the insights to offer at the PRISMA for Abstracts consensus meeting. abstract should only draw conclusions that are substantiated by We are grateful to the other participants of the consensus meeting for data from the full report and analyzed as described in the protocol, their time and interest: Martin Burton, UK Cochrane Centre, UK; Trish rather than selectively emphasising interesting results that were a Groves, BMJ, UK; Alessandro Liberati, Italian Cochrane Centre, Italy; minor or ad hoc component of the analysis. In brief, the abstract Cynthia Mulrow, Annals of Internal Medicine, USA; Melissa Norton, PLOS should be an unbiased representation of the full report. We also Medicine, UK; Elizabeth Wager, Sideview, UK; and to everyone who suggest that peer and editorial review processes related to the responded to the PRISMA for Abstracts survey. abstract should explicitly check this. A particularly difficult area is the Discussion section of an Author Contributions abstract. The checklist includes two items with several elements. Analyzed the data: EMB. Wrote the first draft of the manuscript: EMB. We suggest that authors let the reader know whether they feel their Contributed to the writing of the manuscript: EMB PPG DGA SH HB IC question has been answered, or whether there is still uncertainty PCG TL DT. ICMJE criteria for authorship read and met: EMB PPG before presenting practice and policy implications. These state- DGA SH HB IC PCG TL DT. Agree with manuscript results and ments should be clearly backed by the results given in the abstract, conclusions: EMB PPG DGA SH HB IC PCG TL DT. and by presentation of the strengths and limitations of the evidence in the review. References 1. Bastian H, Glasziou P, Chalmers I (2010) Seventy-five trials and eleven 14. Moher D, Hopewell S, Schulz KF, Montori V, Gotzche PC, et al. (2010) systematic reviews a day: how will we ever keep up? PLoS Med 7(9): e1000326. CONSORT 2010 explanation and elaboration: updated guidelines for doi:10.1371/journal.pmed.1000326. reporting parallel group randomised trials. BMJ 340:c869. doi:10.1136/ 2. Dogan RI, Murray GC, Neveol A, Lu Z (2009) Understanding PubMed user bmj.c869. search behavior through log analysis. Database: Article ID bap018. 15. Hopewell S, Clarke M, Moher D, Wager E, Middleton P, et al. (2008) doi:10.1093/database/bap018. CONSORT for reporting randomized controlled trials in journal and 3. Tovey D (2010) Impact of Cochrane reviews. Cochrane Database Syst Rev 7(8): conference abstracts: explanation and elaboration. PLoS Med 5(1): e20. ED000007. doi:10.1371/journal.pmed.0050020. 4. Ad Hoc Working Group for Critical Appraisal of the Medical Literature (1987) 16. Montori VM, Wilczynski NL, Morgan D, Haynes RB (2005) Optimal search A proposal for more informative abstracts of clinical articles. Ann Intern Med strategies for retrieving systematic reviews from Medline: analytical survey. BMJ 106: 598–604. 330: 68. 5. Haynes RB, Mulrow CD, Huth EJ, Altman DG, Gardner MJ (1990) More 17. Egger M, Juni P, Bartlett C, Holenstein F, Sterne J (2003) How important are informative abstracts revisited. Ann Intern Med 113: 69–76. comprehensive literature searches and the assessment of trial quality in 6. Hartley J (2000) Clarifying the abstracts of systematic literature reviews. Bull systematic reviews? Empirical study. Health Technol Assessment 7(1):1– Med Libr Assoc 88(4): 332–337. 76. 7. Froom P, Froom J (1993) Deficiencies in structured medical abstracts. J Clin 18. Song F, Parekh S, Hooper L, Loke YK, Ryder J, et al. (2010) Dissemination and Epidemiol 46(7): 591–594. publication of research findings: an updated review of related biases. Health Technol Assessment 14(8): iii, ix–xi, 1–193. 8. Hopewell S, Eisinga A, Clarke M (2008) Better reporting of randomized trials in biomedical journal and conference abstracts. J Info Sci 34(2): 162–173. 19. Higgins JPT, Altman DG , Gotzsche PC, Juni P, Moher D, et al. (2011) The 9. Hopewell S, Clarke M, Askie L (2006) Reporting of trials presented in Cochrane Collaboration’s tool for assessing risk of bias in randomised trials. BMJ conference abstracts needs to be improved. J Clin Epidemiol 59: 681–684. 343: d5928. doi:10.1136/bmj.d5928. 10. Beller EM, Glasziou PP, Hopewell S, Altman DG (2011) Reporting of effect 20. Pildal J, Hrobjartsson A, Jorgensen K, Hilden J, Altman D, et al. (2007) Impact direction and size in abstracts of systematic reviews. JAMA 306(18): 1981–1982. of allocation concealment on conclusions drawn from metaanalyses of randomized trials. Int J Epidemiol 36: 847–857. 11. Liberati A, Altman DG, Tetzlaff J, Mulrow C, Gotzsche PC, et al. (2009) The PRISMA statement for reporting systematic reviews and meta-analyses of studies 21. Schulz KF, Grimes DA (2006) The Lancet handbook of essential concepts in that evaluate health care interventions: explanation and elaboration. PLoS Med clinical research. London: Elsevier. 6(7): e1000100. doi:10.1371/journal.pmed.1000100. 22. Hrobjartsson A, Thomsen AS, Emanuelsson F, Tendal B, Hilden J, et al. (2012) 12. Sacks HS, Berrier J, Reitman D, Ancona-Berk VA, Chalmers TC (1987) Meta- Observer bias in randomised clinical trials with binary outcomes: systematic analysis of randomized controlled trials. New Engl J Med 316: 450–455. review of trials with both blinded and non-blinded outcome assessors. BMJ 344: 13. Murphy MK, Black NA, Lamping DL, McKee CM, Sanderson CFB, et al. e1119. doi:10.1136/bmj.e1119. (1998) Consensus development methods, and their use in clinical guideline 23. Ju¨ni P, Altman DG, Egger M (2001) Systematic reviews in health care: Assessing development. Health Technol Assessment 2(3). the quality of controlled clinical trials. BMJ 323: 42–46. PLOS Medicine | www.plosmedicine.org 7 April 2013 | Volume 10 | Issue 4 | e1001419 24. Als-Nielsen B, Gluud LL, Gluud C (2004) Methodological quality and treatment 30. Lexchin J, Bero LA, Djulbegovic B, Clark O (2003) Pharmaceutical industry sponsorship and research outcome and quality: Systematic review. BMJ 326: effects in randomized trials: a review of six empirical studies. 12th Cochrane 1167–1170. Colloquium, Ottawa (Canada). 31. Jørgensen AW, Hilden J, Gøtzsche PC (2006) Cochrane reviews compared with 25. Tierney JF, Stewart LA (2005) Investigating patient exclusion bias in meta- industry supported meta-analyses and other meta-analyses of the same drugs: analysis. Int J Epidemiol 34: 79–87. systematic review. BMJ 333: 782–785. 26. Chan AW, Hro´bjartsson A, Haahr MT, Gøtzsche PC, Altman DG (2004) 32. Booth A, Clarke M, Ghersi D, Moher D, Petticrew M, et al. (2011) Establishing Empirical evidence for selective reporting of outcomes in randomized trials: a minimum dataset for prospective registration of systematic reviews: an comparison of protocols to published articles. JAMA 291: 2457–2465. international consultation. PLoS ONE 6(11): e27319. doi:10.1371/journal.- 27. Guyatt G, Oxman AD, Akl EA, Kunz R, Vist G, et al. (2011) GRADE pone.0027319. guidelines: 1. Introduction – GRADE evidence profiles and summary of findings 33. Hopewell S, Clarke M, Moher D, Wager E, Middleton P, et al. (2008) tables. J Clin Epidemiol 64: 383–394. CONSORT for reporting randomized controlled trials in journal and 28. Antman EM, Lau J, Kupelnick B, Mosteller F, Chalmers TC (1992) A conference abstracts: explanation and elaboration. PLoS Med 5(1): e20. comparison of results of meta-analyses of randomized control trials and doi:10.1371/journal.pmed.0050020. recommendations of clinical experts: treatments for myocardial infarction. 34. Hopewell S, Ravaud P, Baron G, Boutron I (2012) Effect of editors’ JAMA 268: 240–248. implementation of CONSORT guidelines on the reporting of abstracts in high 29. Als-Nielson B (2003) Association of funding and conclusions in randomized drug impact medical journals: interrupted time series analysis. BMJ 344: e4178. trials: a reflection of treatment effect or adverse events? JAMA 290(7): 921–928. doi:10.1136/bmj.e4178. PLOS Medicine | www.plosmedicine.org 8 April 2013 | Volume 10 | Issue 4 | e1001419 http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png PLoS Medicine Public Library of Science (PLoS) Journal

PRISMA for Abstracts: Reporting Systematic Reviews in Journal and Conference Abstracts

PLoS Medicine , Volume 10 (4): e1001419 – Apr 9, 2013
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Guidelines and Guidance; Medicine; Epidemiology; Epidemiological methods; Non-clinical medicine
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Guidelines and Guidance PRISMA for Abstracts: Reporting Systematic Reviews in Journal and Conference Abstracts 1 1 2 2,7 3 Elaine M. Beller *, Paul P. Glasziou , Douglas G. Altman , Sally Hopewell , Hilda Bastian , 4 5 6 6 " Iain Chalmers , Peter C. Gøtzsche , Toby Lasserson , David Tovey , for the PRISMA for Abstracts Group 1 Centre for Research in Evidence-Based Practice, Bond University, Gold Coast, Australia, 2 Centre for Statistics in Medicine, University of Oxford, Oxford, United Kingdom, 3 National Center for Biotechnology Information, National Library of Medicine, Washington DC, United States of America, 4 James Lind Initiative, Oxford, United Kingdom, 5 Nordic Cochrane Centre, Copenhagen, Denmark, 6 Cochrane Editorial Unit, London, United Kingdom, 7 INSERM, Paris, France give more complete information, and facilitate the finding of Introduction information by the reader. When readers screen the title of an article, and parts of its Despite the adoption of structured abstracts, studies of the quality abstract, they try to determine whether or not to devote their of abstracts of clinical trials have demonstrated that improvement is scarce time to reading on. Some may be screening literature to needed [8,9], and a study of systematic review abstracts demon- identify the articles that are systematic reviews. Thus, the main strated that the direction of the effect or association could not be function of an abstract of a systematic review should be to signal its determined in one in four abstracts from the general and specialty systematic methodology. For most readers, the findings described medical literature [10]. The PRISMA Statement [11] gives some in the abstract will also be key, either as the sole part of an article guidance for abstracts, closely linked to commonly used headings in that will be read, or to determine whether reading the full text is structured abstracts. After observing that the quality of abstracts of required. Abstracts of systematic reviews are very important, as systematic reviews is still poor [10], we decided to develop an some readers cannot access the full paper, such that abstracts may extension to the PRISMA Statement to provide guidance on writing be the only option for gleaning research results. This can be abstracts for systematic reviews. We also wanted to provide a because of a pay wall, low Internet download capacity, or if the full checklist enabling the items suggested to fit into any set of headings article is only available in a language not understood by the mandated by a journal or conference submission. reader. Readers in countries where English is not the primary language may have access to an abstract translated to their own Methods for Development of the Checklist language, but not to a translated full text. Conversely, a large proportion of systematic reviews are published by health We established a steering committee (EMB, PPG, SH, DGA). In technology agencies in non-English speaking countries [1], many collaboration with the steering group of the PRISMA Statement [11], of which provide only the abstract in English. we used the Statement to inform our selection of potential items for The predominance of the abstract in biomedical literature use is the checklist of essential items that authors should consider when clear. Within queries to PubMed, most readers look only at titles; reporting the primary results of a systematic review in a journal or only half of searches result in any clicks on content [2]. The conference abstract. The committee generated a list of items from average number of titles clicked on to obtain the abstract or full PRISMA and other sources of guidance and information on text, even after retrieving several searches in a row, is less than five. structured abstracts and abstract composition and reporting Of those clicks, abstracts will be represented about 2.5 times more [7,11,12], which were found using a thorough search of the literature. often than full texts of articles [2]. Even people going straight to a In preparation for a consensus meeting, we used a modified PDF or full text are likely to start, and perhaps end, with reading Delphi consensus survey method [13] to select and reduce the the abstract. The frequency of viewing full texts is somewhat higher among people searching the Cochrane Database of Citation: Beller EM, Glasziou PP, Altman DG, Hopewell S, Bastian H, Systematic Reviews [3], but the same pattern is clear. After the et al. (2013) PRISMA for Abstracts: Reporting Systematic Reviews in Journal and title, the abstract is the most read part of a biomedical article. Conference Abstracts. PLoS Med 10(4): e1001419. doi:10.1371/journal.pmed.1001419 Abstracts can be useful for screening by study type [4]; Published April 9, 2013 facilitating quick assessment of validity [4,5]; enabling efficient This is an open-access article, free of all copyright, and may be freely reproduced, perusal of electronic search results [4,6]; clarifying to which distributed, transmitted, modified, built upon, or otherwise used by anyone for any lawful purpose. The work is made available under the Creative Commons CC0 patients and settings the results apply [4,5]; providing readers and public domain dedication. peer reviewers with explicit summaries of results [5]; facilitating Funding: This research was supported (in part) by the Intramural Research the pre-publication peer review process [7]; and increasing Program of the NIH, National Center for Biotechnology Information (National precision of computerised searches [6,7]. Library of Medicine). The funders had no role in study design, data collection and Structured abstracts were introduced in the medical literature analysis, decision to publish, or preparation of the manuscript. about 25 years ago [4–6]. They provide readers with a series of Competing Interests: TL is employed by The Cochrane Collaboration. TL is an headings, generally about the purpose, methods, results, and editor (unpaid) for the Cochrane Airways Group. The authors have declared that no other competing interests exist. conclusions of the report, and have been adopted by many Abbreviations: PICOS, participants, interventions, comparators, outcomes, and journals and conferences. They act as a prompt to the writer to study designs. * E-mail: [email protected] " Membership of the PRISMA for Abstracts Group is provided in the The Guidelines and Guidance section contains advice on conducting and Acknowledgments. reporting medical research. Provenance: Not commissioned; externally peer reviewed. PLOS Medicine | www.plosmedicine.org 1 April 2013 | Volume 10 | Issue 4 | e1001419 Scope of PRISMA for Abstracts Summary Points The PRISMA for Abstracts checklist focuses on truthful The abstract of a systematic review should provide a representation of a systematic review in an abstract. We developed structured summary that enables a quick assessment of the checklist to help authors report all types of systematic reviews, the review’s validity and applicability, and easy identifi- but recognise that the emphasis is on systematic reviews of cation in electronic searching. evaluations of interventions where one or more meta-analyses are Despite published guidance on writing the abstract in conducted. Authors who address questions on aetiology, diagnostic the PRISMA Statement guiding the reporting of system- test accuracy, or prognosis may need to modify items or include atic reviews in general and elsewhere, evaluations show other items in their abstract to reflect the essentials of the full that reporting of systematic reviews in journal and report. conference abstracts is poor. We developed consensus-based reporting guidelines as The PRISMA for Abstracts Checklist an extension to the PRISMA Statement on good reporting of systematic reviews and meta-analyses in The checklist is shown in Table 1. An explanation for each item abstracts. is given below. Citations for the examples of good reporting are in The PRISMA for Abstracts checklist gives authors a Table 2. framework for condensing their systematic review into the essentials for an abstract that will meet the needs of Section 1: TITLE many readers. Item 1: Title. Identify the report as a systematic review, meta- analysis, or both. number of possible checklist items. Each item was rated by survey Examples: 1a. ‘‘Systematic review and meta-analysis of the participants as ‘‘omit’’, ‘‘possible’’, ‘‘desirable’’, or ‘‘essential’’ to diagnostic and therapeutic role of water-soluble contrast agent in include in the final checklist. From the first round of the survey, adhesive small bowel obstruction.’’ the ranked items were divided into three lists for the second round. 1b. ‘‘Inhaled corticosteroids vs placebo for preventing COPD The first list contained the items with the highest rankings, and [chronic obstructive pulmonary disease] exacerbations: a system- participants for the second round were instructed that these would atic review and metaregression of randomized controlled trials.’’ be contained in the checklist unless they received low rankings in Explanation: The abstract should make it clear that the report is the second round. The second list contained the items with a systematic review, meta-analysis, or both (examples 1a and 1b). moderate rankings, and participants were instructed that these Search filters have been developed to identify systematic reviews items were likely to be removed from the checklist unless they [16], but inclusion of the words ‘‘systematic review’’ or ‘‘meta- received high rankings in the second round. The third list analysis’’ in the title may improve indexing and electronic contained the items with low rankings, and participants were searching. instructed that these items would be removed unless they received We also suggest using informative titles that incorporate the very high rankings in the second round. PICOS approach (participants, interventions, comparators, out- For the third round of the Delphi survey, a draft checklist was comes, and study designs). This provides key information about presented, which included only the items ranked highest in rounds the scope of the systematic review. As including all elements of the one and two. The five next highest-ranked items were then PICOS approach may make the title unwieldy, we suggest presented, giving participants an opportunity to choose to include including the most important of these elements in the title. These these in the checklist as well. might be the elements that make this review unusual, or that assist One hundred and forty-seven participants, who were authors of readers in searching for the review. research on abstracts, established authors of systematic reviews, methodologists or statisticians related to systematic reviews, and Section 2: BACKGROUND journal editors, were invited by email to complete the three rounds of the web-based survey. The response rate was 68% (n = 100) for Item 2: Objectives. the first round. Only those who completed round one were invited The research question including components such as to participate in rounds two and three. The response rate for participants, interventions, comparators, and out- round two was 80% (n = 80) and for round three 88% (n = 88). comes. The results of the survey were reported at a two-day consensus- Examples: 2a. ‘‘To assess the effect on survival of supportive style meeting on 13–14 October 2011, in Oxford, United care and chemotherapy versus supportive care alone in advanced NSCLC [non-small cell lung cancer].’’ Kingdom. Fifteen invited experts attended, most of whom had participated in the survey. The meeting began with a review of the 2b. ‘‘To evaluate the risk of serious asthma-related events literature about abstract structure and content, followed by a among patients treated with formoterol.’’ review of the checklist items as proposed by the survey 2c. ‘‘The objective of this study was to investigate the predictive respondents. Meeting participants discussed the items and agreed value of C-reactive protein in critically ill patients.’’ whether they should be included and how each item should be Explanation: Irrespective of the strength and nature of the worded. results reported in the abstract, readers should be able to assess the Following the meeting, the checklist was distributed to the questions that the review intended to address. The objectives in an participants to ensure it reflected the decisions made. This abstract should convey succinctly the broad aims of the systematic explanatory document was drafted and circulated through several review. Objectives should reflect what the review intended to iterations among members of the writing subcommittee who had evaluate, such as benefit (example 2a), harms (example 2b), all participated in the meeting. We developed this document using association, predictive value (example 2c), of the intervention or the template for the PRISMA Statement [11], which in turn was exposure of interest and the population or context in which this is based on the methods of the CONSORT Group [14,15]. being studied. PLOS Medicine | www.plosmedicine.org 2 April 2013 | Volume 10 | Issue 4 | e1001419 Table 1. The PRISMA for Abstracts Checklist. TITLE 1. Title: Identify the report as a systematic review, meta-analysis, or both. BACKGROUND 2. Objectives: The research question including components such as participants, interventions, comparators, and outcomes. METHODS 3. Eligibility criteria: Study and report characteristics used as criteria for inclusion. 4. Information sources: Key databases searched and search dates. 5. Risk of bias: Methods of assessing risk of bias. RESULTS 6. Included studies: Number and type of included studies and participants and relevant characteristics of studies. 7. Synthesis of results: Results for main outcomes (benefits and harms), preferably indicating the number of studies and participants for each. If meta-analysis was done, include summary measures and confidence intervals. 8. Description of the effect: Direction of the effect (i.e., which group is favoured) and size of the effect in terms meaningful to clinicians and patients. DISCUSSION 9. Strengths and Limitations of evidence: Brief summary of strengths and limitations of evidence (e.g., inconsistency, imprecision, indirectness, or risk of bias, other supporting or conflicting evidence). 10. Interpretation: General interpretation of the results and important implications. OTHER 11. Funding: Primary source of funding for the review. 12. Registration: Registration number and registry name. doi:10.1371/journal.pmed.1001419.t001 (example 3d). This is important as inclusion, or not, of studies Section 3: METHODS published in languages other than English (examples 3c and 3d), Item 3: Eligibility criteria. unpublished data, or older data can influence the estimates of Study and report characteristics used as criteria for effect or association in meta-analyses [17,18]. inclusion. Item 4: Information sources. Examples – study characteristics: 3a. ‘‘We included randomised Key databases searched and date of last search. controlled trials testing the combination of long-acting ß - agonists Examples: 4a. ‘‘PubMed, ERIC and Cochrane Reviews in combination with inhaled corticosteroids (ICS) versus the same databases from January 1980 to November 2007 were searched or an increased dose of ICS for a minimum of at least 28 days in for studies…’’ children and adolescents with asthma.’’ 4b. ‘‘We searched MEDLINE, EMBASE, the Cochrane 3b. ‘‘… randomized trials of compression stockings versus no Central Register of Controlled Trials (CENTRAL), other trial stockings in passengers on flights lasting at least four hours. Trials registries and product information sheets through June 2008.’’ in which passengers wore a stocking on one leg but not the other, Explanation: The abstract should briefly indicate how thorough or those comparing stockings and another intervention were also and up-to-date the search was by listing key databases searched, eligible.’’ and the date range (example 4a) or date of last search (example Examples – report characteristics: 3c. ‘‘… studies published in 4b). We recommend that if there are three or fewer databases, list English, French, Spanish, Italian and German between 1966 and them all; otherwise list the three that provided the majority of July, 2008 [were included].’’ included studies. 3d. ‘‘We performed a literature search of trials using Item 5: Risk of bias assessment. MEDLINE (January 1966–December 2001) … we retrieved Methods for assessing risk of bias. English- and non-English-language articles for review… we searched for both published and unpublished trials…’’ Example: 5a. ‘‘Risk of bias was assessed regarding randomisa- Explanation: One of the key features distinguishing a systematic tion, allocation sequence concealment, blinding, incomplete outcome data, selective outcome reporting, and other biases.’’ review from a narrative review is the pre-specification of eligibility criteria for including and excluding studies. A clear description of Explanation: Problems in the design and conduct of individual these allows the readers to assess the applicability of the systematic studies can raise questions about the validity of their findings [19]. review findings [11]. Study eligibility characteristics are likely to For example, reports of randomised trials with inadequate include the study questions (PICOS)—types of participants allocation sequence concealment are more likely to show included in the studies (often based on a common clinical exaggerated treatment effects [20]. And non-blinded assessors of diagnosis), the intervention of prime interest and possibly the subjective outcomes generate substantially biased effect estimates specific comparison intervention, the main outcome(s) being [21,22]. It is therefore an important part of a systematic review to assessed—and acceptable study designs (examples 3a and 3b). assess the validity of individual studies, and the risk that they will Eligibility criteria for reports may also include the language of overestimate the true intervention effect. Authors should describe publication, the publication status (e.g., whether to include any methods they used to assess the risk of bias in the included unpublished materials and abstracts) and the year of publication studies (example 5a). PLOS Medicine | www.plosmedicine.org 3 April 2013 | Volume 10 | Issue 4 | e1001419 Table 2. List of references used as examples. Example Number Citation 1a. Branco BC, Barmparas G, Schuriger B, Inaba K, et al. (2010) Systematic review and meta-analysis of the diagnostic and therapeutic role of water-soluble contrast agent in adhesive small bowel obstruction. British Journal of Surgery 97: 470–478. 1b. Agarwal R, Aggarwal AN, Gupta D, Jindal SK (2010) Inhaled corticosteroids vs placebo for preventing COPD exacerbations: a systematic review and metaregression of randomized controlled trials. Chest 137(2): 318–325. 2a. Non-Small Cell Lung Cancer Collaborative Group (2010) Chemotherapy and supportive care versus supportive care alone for advanced non-small cell lung cancer. Cochrane Database of Systematic Reviews. Issue 5, Art. No. CD007309. DOI:10.1002/14651858.CD007309.pub2. 2b. Kemp J, Armstrong L, Wan Y, Alagappan VKT, Ohlssen D, Pascoe S (2011) Safety of formoterol in adults and children with asthma: a meta- analysis. Annals of Asthma, Allergy and Immunology 107(1): 71–78. 2c. Zhang Z, Ni H (2011) C-reactive protein as a predictor of mortality in critically ill patients: a meta-analysis and systematic review. Anaesthesia and Intensive Care 39(5): 854–861. 3a. Chroinin M, Lasserson TJ, Greenstone I, Ducharme FM (2009) Addition of long-acting beta-agonists to inhaled corticosteroids for chronic asthma in children. Cochrane Database of Systematic Reviews Issue 3. Art. No. CD007949. DOI:10.1002/14651858.CD007949. 3b. Clarke MJ, Hopewell S, Juszczak E, Eisinga A, Kjeldstrøm M (2006) Compression stockings for preventing deep vein thrombosis in airline passengers. Cochrane Database of Systematic Reviews. Issue 2, Art. No. CD004002. DOI:10.1002/14651858.CD004002.pub2. 3c. Steinhart AH, Ewe K, Griffiths AM, Modigliani R, Thomsen OO (2003) Corticosteroids for maintenance of remission in Crohn’s disease. Cochrane Database of Systematic Reviews Issue 4. Art. No. CD000301. DOI:10.1002/14651858.CD000301. 3d. Trinh NH, Hoblyn J, Mohanty S, Yaffe K (2003) Efficacy of cholinesterase inhibitors in the treatment of neuropsychiatric symptoms and functional impairment in Alzheimer disease: a meta-analysis. Journal of the American Medical Association 289(2): 210–216. 4a. Bonuck KA, Freeman K, Henderson J (2009) Growth and growth biomarker changes after adenotonsillectomy: systematic review and meta-analysis. Archives of Disease in Childhood 94: 83–91. DOI:10.1136/adc.2008.141192. 4b. Loke YK, Singh S, Furberg CD (2009) Long-term use of thiazolidinediones and fractures in type 2 diabetes: a meta-analysis. CMAJ 180(1): 32–39. 5a. Cho S-H, Lee H, Ernst E (2010) Acupuncture for pain relief in labour: a systematic review and meta-analysis. BJOG 117: 907–920. 6a. Huss A, Scott P, Stuck AE, Trotter C, Egger M (2009) Efficacy of pneumococcal vaccination in adults: a meta-analysis. CMAJ 180(1): 48–58. 6b. Alexander LD, Gilman DRD, Brown DR, Brown JL, Houghton PE (2010) Exposure to low amounts of ultrasound energy does not improve soft tissue shoulder pathology: a systematic review. Physical Therapy 90(1): 14–25. 7a. Al-Majed NS, McAlister FA, Bakal JA, Ezekowitz JA (2011) Meta-analysis: cardiac resynchronization therapy for patients with less symptomatic heart failure. Annals of Internal Medicine 154: 401–412. 7b. Wilson A, Gallos ID, Plana N, Lissauer D, Khan KS, Zamora J et al (2011) Effectiveness of strategies incorporating training and support of traditional birth attendants on perinatal and maternal mortality: meta-analysis. BMJ 343: d7102. DOI: 10.1136/bmj.d7102 7c. Gillies M, Palmateer N, Hutchinson S, Ahmed S, Taylor A, Goldberg D (2010) The provision of non-needle/syringe drug injecting paraphernalia in the primary prevention of HCV among IDU: a systematic review. BMC Public Health 10: 721. 8a. Jolly SS, Amlani S, Hamon M, Yusuf S, Mehta SR (2009) Radial versus femoral access for coronary angiography or intervention and the impact on major bleeding and ischemic events: a systematic review and meta-analysis of randomized trials. American Heart Journal 157(1): 132–140. 8b. Lam LL, Cameron PA, Schneider HG, Abramson MJ, Muller C, et al. (2010) Meta-analysis: effect of B-type natriuretic peptide testing on clinical outcomes in patients with acute dyspnea in the emergency setting. Annals of Internal Medicine 153(11): 728–735. 8c. Madsen MV, Gøtzsche PC, Hrobjartsson A (2009) Acupuncture treatment for pain: systematic review of randomised clinical trials with acupuncture, placebo acupuncture, and no acupuncture groups. BMJ 338: a3115. DOI:10.1136/bmj.a3115. 9a. Santangeli P, Di Biase L, Dello Russo A, Casella M, Bartoletti S et al (2010) Meta-analysis: age and effectiveness of prophylactic implantable cardioverter-defibrillators. Annals of Internal Medicine 153(9): 592–599. 9b. Ceglia L, Lau J, Pittas AG (2006) Meta-analysis: efficacy and safety of inhaled insulin therapy in adults with diabetes mellitus. Annals of Internal Medicine 145(9): 665–675. 9c. Lin J S, O’Connor E, Whitlock EP, Beil TL (2010) Behavioral counseling to promote physical activity and a healthful diet to prevent cardiovascular disease in adults: a systematic review for the U.S. Preventive Services Task Force. Annals of Internal Medicine 53(11): 736– 9d. Zoungas S, Ninomiya T, Huxley R, Cass A, Jardine M, et al. (2009) Systematic review: sodium bicarbonate treatment regimens for the prevention of contrast-induced nephropathy. Annals of Internal Medicine 151: 631–638. 10a. Chandra D, Parasini E, Mozaffarian D (2009) Meta-analysis: travel and risk for venous thromboembolism. Annals of Internal Medicine 151(3): 180–190. 10b. Thomson H, Thomas S, Sellstrom E, Petticrew M (2009) The health impacts of housing improvement: a systematic review of intervention studies from 1887 to 2007. American Journal of Public Health 99 Suppl 3: S681–S692. 10c. Wells G, Parkash R, Healey JS, Talajic M, Arnold M, Sullivan S, et al. (2011) Cardiac resynchronization therapy: a meta-analysis of randomized controlled trials. CMAJ 183(4): 421–429. DOI:10.1503/cmaj.101685. 11a. Levy G, Hill MJ, Ramirez CI, Correa L, Ryan ME, et al. (2012) The use of follicle flushing during oocyte retrieval in assisted reproductive technologies: a systematic review and meta-analysis. Human Reproduction 27(8): 2373–2379. 11b. McKnight RF, Adida M, Budge K, Stockton S, Goodwin GM, et al. (2012) Lithium toxicity profile: a systematic review and meta-analysis. Lancet 379(9817): 721–728. DOI:10.1016/S0140-6736(11)61516-X. PLOS Medicine | www.plosmedicine.org 4 April 2013 | Volume 10 | Issue 4 | e1001419 Table 2. Cont. Example Number Citation 12a. Timmons BW, Leblanc AG, Carson V, Connor Gorber S, Dillman C, et al. (2012) Systematic review of physical activity and health in the early years (aged 0–4 years). Applied Physiology, Nutrition and Metabolism 37(4): 773–792. 12b. Stradling C, Chen YF, Russell T, Connock M, Thomas GN, et al. (2012) The effects of dietary intervention on HIV dyslipidaemia: a systematic review and meta-analysis. PLoS ONE 7(6):e38121. Epub 2012 Jun 11. doi:10.1371/journal.pmed.1001419.t002 Many tools exist for assessing the overall risk of bias in included of non-N/S [non-needle/syringe] injecting paraphernalia associ- studies, including scales, checklists and individual components ated with use of NSP [needle and syringe exchange programmes] [23]. Most tools are scales in which various components of quality or SIF [safer injection facilities].’’ Explanation: The results for the main outcomes should be given are scored and combined to give a summary score. This approach can be seriously misleading, however, and should be discouraged. in the abstract. If meta-analyses have been done, include for each the summary measure (estimated effect) and confidence interval. If A preferred approach requires authors to specify which individual methodological components they will assess and to provide a the intention had been to perform meta-analysis, but no meta- analysis was done for one or more main outcomes, the reasons description and judgment for each component for each of the should be stated (e.g., heterogeneity too great). studies assessed [19]. For randomised trials, common components The abstract should make clear the protocol-defined, pre- include: appropriate generation of the allocation sequence [24], specified importance of each outcome reported, and should not concealment of the allocation sequence [20], blinding of partic- report only those outcomes that have statistically significant or ipant and health care providers, blinding of outcome assessors clinically important results. [22], assessment of incomplete outcome data [25], and selective Where possible, given space limitations, the number of studies outcome reporting [26]. and participants for each main outcome should be stated, particularly if only a small proportion of the total number of Section 4: RESULTS studies or patients in the systematic review contributed informa- Item 6: Included studies. tion on a particular outcome. Number and type of included studies and partici- If there are no summary measures, some numerical data may pants, and relevant characteristics of studies. still be given (example 7c), although authors should be wary of Examples: 6a. ‘‘We included 22 trials involving 101 507 making this in the form of ‘‘vote counting’’ where the number of participants: 11 trials reported on presumptive pneumococcal ‘‘positive’’ and ‘‘negative’’ studies is given. Vote counting takes no pneumonia, 19 on all-cause pneumonia and 12 on all-cause account of weighting of studies according to the amount of mortality. The current 23-valent vaccine was used in 8 trials.’’ information they contain [27]. 6b. ‘‘Eight studies included in this review (n = 586 patients, Item 8: Description of effect. median PEDro score = 8.0/10) evaluated various parameters, Direction of the effect (i.e., which group is favoured) including the duration of patients’ symptoms (0–12 months), duty and size of the effect in terms meaningful to patients and cycle (20% and 100%), intensity (0.1–2.0 W/cm2), treatment time clinicians. per session (4.5–15.8 minutes), number of treatments (6–39), and Examples: 8a. ‘‘Radial access reduced major bleeding by 73% total energy applied per treatment (181–8,152 J).’’ compared to femoral access (0.05% vs 2.3%, OR 0.27 [95% CI Explanation: The number of studies, number of participants, 0.16, 0.45], P,0.001).’’ and characteristics of the included studies (examples 6a and 6b) 8b. ‘‘Length of hospital and critical care unit stay were both enable readers to gauge the validity and applicability of the modestly reduced in the tested group compared with the control systematic review’s results. These characteristics might include group, with a mean difference of 21.22 day (CI, 22.31 to 20.14 descriptors of the participants (e.g., age, severity of disease), range day) and 20.56 day (CI, 21.06 to 20.05 day), respectively.’’ of interventions used (e.g., dose and frequency of drug adminis- 8c. ‘‘A small difference was found between acupuncture and tration), and measurement of outcomes (e.g., follow-up times). placebo acupuncture: standardised mean difference 20.17 (95% Item 7: Synthesis of results. confidence interval 20.26 to 20.08)… [in favour of acupunc- Results for main outcomes (benefits and harms), ture]…, corresponding to 4 mm (2 mm to 6 mm) on a 100 mm preferably indicating the number of studies and partic- visual analogue scale.’’ ipants for each. If meta-analysis was done, include Explanation: The results should summarise the main outcomes summary measures and confidence intervals. in words and numbers. The wording should indicate the direction Examples: 7a. ‘‘… CRT [cardiac resynchonization therapy] of the effect (e.g., lower, fewer, reduced; greater, more, increased) reduced all-cause mortality (6 trials, 4572 participants; risk ratio and the size of the effect using familiar units such as percentages, [RR], 0.83 [95% CI, 0.72 to 0.96]) and heart failure hospitaliza- days, or kilograms. Example 8a makes clear the size of the effect tions (4 trials, 4349 participants; RR, 0.71 [CI, 0.57 to 0.87]) even for readers who have difficulty interpreting relative risks and without improving functional outcomes or quality of life.’’ confidence intervals. When a percentage is used, the baseline risk 7b. ‘‘Six studies reported on maternal mortality and our meta- should also be shown, which allows the reader to see what the analysis showed a non-significant reduction (three randomised absolute benefit or harm is, and calculate whichever measures they trials, relative risk 0.79, 0.53 to 1.05, P = 0.12; three non- choose (example 8a). Authors should take care to make it clear randomised studies, 0.80, 0.44 to 1.15, P = 0.26).’’ whether the reported measure is an absolute or a relative one (e.g., 7c. ‘‘Eight studies presented adjusted odds ratios, ranging from where percentage is used as the units of measurement). Where 0.3 to 0.9, suggesting a reduced likelihood of self-reported sharing possible, continuous outcome measures should be expressed in PLOS Medicine | www.plosmedicine.org 5 April 2013 | Volume 10 | Issue 4 | e1001419 familiar units (example 8b), particularly when the standardised If there is insufficient evidence from well-conducted studies to mean difference is used (example 8c). answer the review’s question, this should be made clear to the reader. When the results are not statistically significant, authors should distinguish between those where there is insufficient Section 5: DISCUSSION evidence to rule out a difference between treatments (wide Item 9: Strengths and limitations of evidence. confidence interval), and those which have sufficient evidence Brief summary of strength and limitations of evidence that an important difference is unlikely (narrow confidence (e.g., inconsistency, imprecision, indirectness, or risk of interval). bias, other supporting or conflicting evidence). If the conclusions of the review differ substantially from previous Examples: 9a. ‘‘Four potentially eligible trials were not included systematic reviews, then some explanation might also be provided. in the meta-analysis because mortality data by age group were not Reference could be made to known ongoing studies that have the available.’’ potential to change the result of the review. Possible implications 9b. ‘‘All trials were open label, which may introduce bias. Most for policy and practice should be stated. of the trials were of 24 weeks’ duration or less, limiting assessment of long-term safety.’’ 9c. ‘‘Meta-analyses for some outcomes had large statistical Section 6: OTHER heterogeneity or evidence for publication bias. Only 11 trials Item 11: Funding. followed outcomes beyond 12 months.’’ Primary source of funding for the review. 9d. ‘‘Meta-regression showed that small, poor-quality studies Examples: 11a. ‘‘This work was supported, in part, by the that assessed outcomes soon after radiocontrast administration Program in Reproductive and Adult Endocrinology, NICHD, were more likely to suggest benefit (P,0.05 for all).’’ NIH, Bethesda, MD. The authors have no competing interests to Explanation: The abstract should briefly describe the strengths declare.’’ and limitations of the evidence across studies [28]. Limitations 11b. ‘‘Funding: National Institute for Health Research may include: risk of bias common to many or all studies, such as Programme Grant for Applied Research.’’ lack of blinding for subjective outcomes (example 9b) or Explanation: Studies of the relationship between pharmaceuti- unavailability of data (example 9a); inconsistency of effect or cal company funding and results of clinical trials have shown that association, as demonstrated by high heterogeneity (examples 9c sponsored studies are more likely to have outcomes favouring the and 9d); imprecision, e.g., due to few events or small sample sizes; sponsor [29,30]. This is also the case for systematic reviews [31]. indirectness of the evidence, such as the use of an intermediate or Therefore, the abstract should indicate whether the sponsor of the short-term outcome (examples 9b and 9c); and likely publication research or the researchers might have a conflict of interest in bias (example 9c). Potential strengths of the overall body of respect of the findings of the systematic review, for example, as the evidence that might apply for a particular outcome of a systematic manufacturer of the intervention being evaluated (examples 11a review include: a large effect (example 8a); demonstration of a and 11b). The abstract should include the main source of funding dose-response relationship (example 10a, below); and that all for the systematic review, whether from host institutions or from biases would be likely to reduce the effect rather than increase it. external bodies. One or more of these strengths and limitations may apply to each Item 12: Registration. of the outcomes of the systematic review being described in the Registration number and registry name. abstract. Some of this information may be combined with item 6, Examples: 12a. ‘‘PROSPERO registration: CRD42011 above, when describing the included studies, however a summary 001243.’’ of the overall strengths and limitations of the evidence might also 12b. ‘‘PROSPERO 2011:CRD42011001329.’’ be helpful. Explanation: Registration of systematic reviews provides a Item 10: Interpretation. record of reviews that have been initiated, even if they have not General interpretation of the results and important been published. It is therefore a means of alerting researchers to implications. systematic reviews that are in progress, and serves as a public Examples: 10a. ‘‘Travel is associated with a nearly 3-fold higher record of the proposed systematic review. It also helps to detect risk for VTE [venous thromoboembolism], with a dose-response reporting bias by enabling better identification of unpublished relationship of 18% higher risk for each 2-hour increase in travel systematic reviews, and also to compare the methods or outcomes duration.’’ reported in published reviews with those originally proposed in 10b. ‘‘Housing improvements, especially warmth improve- registered protocols [32]. The abstract should record the name of ments, can generate health improvements; there is little evidence the database with which the review is registered, and the of detrimental health impacts. The potential for health benefits registration number. Cochrane reviews are an exception to this may depend on baseline housing conditions and careful targeting requirement, as they are preceded by a peer reviewed protocol of the intervention. Investigation of socioeconomic impacts that is published in the Cochrane Library and can be downloaded associated with housing improvement is needed to investigate from there. the potential for longer-term health impacts.’’ 10c. ‘‘The cumulative evidence is now conclusive that the Discussion addition of cardiac resynchronization to optimal medical therapy or defibrillator therapy significantly reduces mortality among The title of a systematic review is its first signal of its relevance to patients with heart failure.’’ potential readers. Few titles will entice a reader to invest additional time, but when they do, they ordinarily start—and quite often Explanation: Remembering that some readers may struggle with interpreting the statistical results, an overall summary of the end—with the abstract. The first impression is therefore crucial. main effects—positive or negative—should be given (example We strongly recommend the use of structured abstracts for 10a). This could include an indication of what is clear (example reporting systematic reviews, as does the PRISMA Statement [11]. 10c), what important uncertainties remain (example 10b), and We recognise that journals have developed their own set of whether there is ongoing research addressing these. headings that are considered appropriate for reporting systematic PLOS Medicine | www.plosmedicine.org 6 April 2013 | Volume 10 | Issue 4 | e1001419 reviews, and it is not our intention to suggest changes to these We encourage journals and conference organisers to endorse headings, but to recommend what should be reported under them. the use of PRISMA for Abstracts, in a similar way to CONSORT The order of items and the headings are therefore flexible. For for Abstracts [33]. This may be done by modifying their example, the strengths and limitations may be stated at the end of instructions to authors and including a link to the checklist on the Results, under a separate heading, or with the Discussion or their website. It has been demonstrated that the number of Conclusions, depending on journal requirements. It may also be checklist items reported is improved in journals that require possible to combine items from the checklist into one sentence. For checklist completion as part of the submission process [34]. example, limitations may be combined with a description of the Abstracts should not replace full articles in informing decision included studies (i.e., items 6 and 9 from the checklist). making, but for time-pressed readers and those with limited access We have suggested reporting a minimum set of items. We do to full text reports, the abstract must stand alone in presenting a not advocate that abstracts replace full articles in informing clear and truthful account of the research. The PRISMA for decision making, but we recognise that for many time-pressed Abstracts checklist will guide authors in presenting an abstract that readers, or for those with limited access to the full texts of reports, facilitates a quick assessment of review validity, an explicit it is important that abstracts contain as much information as is summary of results, facilitates pre-publication or conference feasible within the word limit of abstracts. Indeed, for readers who selection peer review, and enables efficient perusal of electronic do not understand the language of publication of the article, the search results. translated abstract may have far more relevance than the full-text article. Acknowledgments A checklist is not sufficient to ensure good abstract writing. For example, the abstract should clearly and truthfully reflect the full We dedicate this paper to the memory of Alessandro Liberati who, among many important achievements, was instrumental in the development and report, and not selectively report results that are statistically implementation of the PRISMA Statement, and had many thoughtful significant while not referring to those that were not. Similarly, the insights to offer at the PRISMA for Abstracts consensus meeting. abstract should only draw conclusions that are substantiated by We are grateful to the other participants of the consensus meeting for data from the full report and analyzed as described in the protocol, their time and interest: Martin Burton, UK Cochrane Centre, UK; Trish rather than selectively emphasising interesting results that were a Groves, BMJ, UK; Alessandro Liberati, Italian Cochrane Centre, Italy; minor or ad hoc component of the analysis. In brief, the abstract Cynthia Mulrow, Annals of Internal Medicine, USA; Melissa Norton, PLOS should be an unbiased representation of the full report. We also Medicine, UK; Elizabeth Wager, Sideview, UK; and to everyone who suggest that peer and editorial review processes related to the responded to the PRISMA for Abstracts survey. abstract should explicitly check this. A particularly difficult area is the Discussion section of an Author Contributions abstract. The checklist includes two items with several elements. Analyzed the data: EMB. Wrote the first draft of the manuscript: EMB. We suggest that authors let the reader know whether they feel their Contributed to the writing of the manuscript: EMB PPG DGA SH HB IC question has been answered, or whether there is still uncertainty PCG TL DT. ICMJE criteria for authorship read and met: EMB PPG before presenting practice and policy implications. These state- DGA SH HB IC PCG TL DT. Agree with manuscript results and ments should be clearly backed by the results given in the abstract, conclusions: EMB PPG DGA SH HB IC PCG TL DT. and by presentation of the strengths and limitations of the evidence in the review. References 1. Bastian H, Glasziou P, Chalmers I (2010) Seventy-five trials and eleven 14. Moher D, Hopewell S, Schulz KF, Montori V, Gotzche PC, et al. (2010) systematic reviews a day: how will we ever keep up? PLoS Med 7(9): e1000326. CONSORT 2010 explanation and elaboration: updated guidelines for doi:10.1371/journal.pmed.1000326. reporting parallel group randomised trials. BMJ 340:c869. doi:10.1136/ 2. Dogan RI, Murray GC, Neveol A, Lu Z (2009) Understanding PubMed user bmj.c869. search behavior through log analysis. Database: Article ID bap018. 15. Hopewell S, Clarke M, Moher D, Wager E, Middleton P, et al. (2008) doi:10.1093/database/bap018. CONSORT for reporting randomized controlled trials in journal and 3. Tovey D (2010) Impact of Cochrane reviews. 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PLoS Medicine – Public Library of Science (PLoS) Journal

Published: Apr 9, 2013

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