Search and selection methodology of systematic reviews in orthodontics (2000-2004)

Do pooled estimates from orthodontic meta-analyses change depending on the meta-analysis approach? A meta-epidemiological study

BACKGROUND

In meta-analyses involving a few trials, appropriate measures should be employed to assess between-study heterogeneity. When the number of studies is less than five and heterogeneity is evident, the Hartung and Knapp (HK) correction should be used. The aim of this study was to compare the reported estimates of published orthodontic meta-analyses with the pooled effect size estimates and prediction intervals (PI) calculated using eight heterogeneity estimators and corrected using the HK correction.

MATERIAL AND METHODS

Systematic reviews (SRs) published between 2017 and 2022 in four orthodontic journals and the Cochrane Database of Systematic Reviews with a meta-analysis of at least three studies were sourced. Study characteristics were extracted at the SR and the outcome/meta-analysis levels. All selected meta-analyses were re-analysed by fitting a random-effects model using eight different heterogeneity estimators, both with and without the HK correction. For each meta-analysis, the overall estimate, along with its standard error, the P-value, and the corresponding 95% confidence interval (CI), the between-study variance (tau2), the I2 statistic, and the PI were calculated.

RESULTS

One-hundred-six SRs were analysed. The most prevalent type of SR was non-Cochrane (95.3%), and the most used meta-analyses synthesis model was the random effect (83.0%). The median number of primary studies was 6 (interquartile range: 5, range: 3-45). The between-study variance was reported in most of the eligible meta-analyses (91.5%), but the type of heterogeneity estimator was reported in only one of them (0.9%). In 5 of 106 meta-analyses (4.7%), the HK correction was applied to adjust the CI of the pooled estimate. The percentage of statistically significant results, which became statistically non-significant, ranged from 16.7% to 25%, depending on the heterogeneity estimator. As the number of studies in a meta-analysis increased, the difference between corrected and uncorrected CIs reduced. Based on the PIs, more than half of the meta-analyses having statistically significant results are likely to change in the future, suggesting the result of the meta-analysis is not conclusive.

CONCLUSIONS

The statistical significance of pooled estimates from meta-analyses with at least three studies is sensitive to the HK correction, the heterogeneity variance estimator, and PIs. Clinicians should be aware of the clinical implications of not appropriately assessing the effect of the small number of studies and the between-study heterogeneity when interpreting results from meta-analyses.

Reporting of the methodological quality of search strategies in orthodontic quantitative systematic reviews

BACKGROUND

This study aimed to assess the reporting of the methodological quality of search strategies undertaken in orthodontic quantitative systematic reviews (SRs) and hence their reproducibility.

MATERIALS AND METHODS

A search of a single electronic database (Medline via PubMed) was undertaken to identify interventional orthodontic SRs with meta-analysis published within a 10-year period. The Cochrane Library of Systematic Reviews was also sourced. Full articles were reviewed by two assessors against the eligibility criteria. The reporting quality of each search strategy was assessed using a previously validated checklist with a score of 1 or 2 given for each of the eight items. Cumulative totals were calculated. Guided by previous research, the authors agreed the following cut-offs to categorize the overall level of quality: 8-10 (poor), 10-12 (fair), and greater than 13 (good).

RESULTS

A total of 127 SRs were analysed. The overall median quality score for the reporting of the search strategy was 14 [interquartile range (IQR): 13-15]. Cochrane SRs and those originating in Europe received higher aggregate scores, whereas no difference was evident based on Prospero registration. The continent of the corresponding author predicated the overall score. Non-Cochrane reviews achieved lower overall scores compared to Cochrane reviews (-1.0, 95% confidence interval: -1.65, -0.34, P = 0.003). The most frequently searched database was EMBASE (N = 93) and the median number of authors was 5 (IQR 4-6). Authors of 26.8% of SRs searched the grey literature. Language restrictions were applied to the search strategies of 88 (69.3%) SRs.

CONCLUSIONS

The reporting quality of search strategies undertaken in orthodontic SRs is at a good level but differences between Cochrane and non-Cochrane reviews currently exist. The reporting of searching of the grey literature and application of no language restrictions can be improved.

Development of an efficient search filter to retrieve systematic reviews from PubMed

Objective:

Locating systematic reviews is essential for clinicians and researchers when creating or updating reviews and for decision-making in health care. This study aimed to develop a search filter for retrieving systematic reviews that improves upon the performance of the PubMed systematic review search filter.

Methods:

Search terms were identified from abstracts of reviews published in Cochrane Database of Systematic Reviews and the titles of articles indexed as systematic reviews in PubMed. Both the precision of the candidate terms and the number of systematic reviews retrieved from PubMed were evaluated after excluding the subset of articles retrieved by the PubMed systematic review filter. Terms that achieved a precision greater than 70% and relevant publication types indexed with MeSH terms were included in the filter search strategy.

Results:

The search strategy used in our filter added specific terms not included in PubMed's systematic review filter and achieved a 61.3% increase in the number of retrieved articles that are potential systematic reviews. Moreover, it achieved an average precision that is likely greater than 80%.

Conclusions:

The developed search filter will enable users to identify more systematic reviews from PubMed than the PubMed systematic review filter with high precision.

Impact of the COVID-19 pandemic on in-hospital mortality in cardiovascular disease: a meta-analysis

Aims 

The COVID-19 pandemic has resulted in excess mortality due to both COVID-19 directly and other conditions, including cardiovascular (CV) disease. We aimed to explore the excess in-hospital mortality, unrelated to COVID-19 infection, across a range of CV diseases.

Methods and results 

A systematic search was performed for studies investigating in-hospital mortality among patients admitted with CV disease without SARS-CoV-2 infection compared with a period outside the COVID-19 pandemic. Fifteen studies on 27 421 patients with CV disease were included in the analysis. The average in-hospital mortality rate was 10.4% (n = 974) in the COVID-19 group and 5.7% (n = 1026) in the comparator group. Compared with periods outside the COVID-19 pandemic, the pooled risk ratio (RR) demonstrated increased in-hospital mortality by 62% during COVID-19 [95% confidence interval (CI) 1.20–2.20, P = 0.002]. Studies with a decline in admission rate >50% during the COVID-19 pandemic observed the greatest increase in mortality compared with those with <50% reduction [RR 2.74 (95% CI 2.43–3.10) vs. 1.21 (95% CI 1.07–1.37), P < 0.001]. The observed increased mortality was consistent across different CV conditions (P = 0.74 for interaction).

Conclusions 

In-hospital mortality among patients admitted with CV diseases was increased relative to periods outside the pandemic, independent of co-infection with COVID-19. This effect was larger in studies with the biggest decline in admission rates, suggesting a sicker cohort of patients in this period. However, studies were generally poorly conducted, and there is a need for further well-designed studies to establish the full extent of mortality not directly related to COVID-19 infection.

Therapies to limit myocardial injury in animal models of myocarditis: a systematic review and meta-analysis

Current myocarditis guidelines do not advocate treatment to prevent myocardial injury and scar deposition in patients with myocarditis and normal left ventricular ejection fraction. We aimed to ascertain the utility of beta blockers, calcium channel blockers and antagonists of the renin–angiotensin system in ameliorating myocardial injury, scar formation and calcification in animal in vivo models of myocarditis. The project was prospectively registered with the PROSPERO database of systematic reviews (CRD42018089336). Primary outcomes (necrosis, fibrosis and calcification) were meta-analysed with random-effects modelling. 52 studies were systematically reviewed. Meta-analysis was performed compared with untreated controls. In each study, we identified all independent comparisons of treatment versus control groups. The pooled weighted mean difference (WMD) indicated treatment reduced necrosis by 16.9% (71 controlled analyses, 95% CI 13.2–20.7%; P < 0.001), however there was less evidence of an effect after accounting for publication bias. Treatment led to a 12.8% reduction in fibrosis (73 controlled analyses, 95% CI 7.6–18.0%; P < 0.001). After accounting for publication bias this was attenuated to 7.8% but remained significant. Treatment reduced calcification by 4.1% (28 controlled analyses, 95% CI 0.2–8.0%; P < 0.0395). We observed significant heterogeneity in effect size in all primary endpoints, which was predominantly driven by differences between drug categories. Beta blockers and angiotensin-converting enzyme (ACE) inhibitors were the only agents that were effective for both necrosis and fibrosis, while only ACE inhibitors had a significant effect on calcification. This study provides evidence for a role for ACE inhibitors and beta blockers to prevent myocardial injury and scar deposition in in vivo models of myocarditis. There is a need for further well-designed studies to assess the translational application of these treatments.

Systematic reviews in orthodontics: Impact of the PRISMA for Abstracts checklist on completeness of reporting

INTRODUCTION

This study evaluated and compared the completeness of reporting of abstracts of orthodontics systematic reviews before and after the publication of the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) extension for Abstracts Checklist (PRISMA-A).

METHODS

Abstracts of systematic reviews and meta-analyses in orthodontics published in PubMed, Latin American and Caribbean Health Sciences Literature, and the Cochrane Database of Systematic Reviews databases before March 23, 2018, that met the predefined inclusion and exclusion criteria, were evaluated using the 12 items of PRISMA-A, scoring each item from 0 to 2. Abstracts were classified into 2 groups: before and after publication of the PRISMA-A checklist. Three calibrated evaluators (intraclass correlation coefficient and kappa > 0.8) assessed the scores for compliance with the checklist. The number of authors, country of affiliation of the first author, performance of meta-analysis, and topic of the article were recorded. A regression analysis was performed to assess the associations between abstract characteristics and the PRISMA-A scores.

RESULTS

Of 1034 abstracts evaluated, 389 were included in the analysis. The mean PRISMA-A score was 53.39 (95% CI, 51.83-54.96). The overall score for studies published after the publication of the checklist was significantly higher than for studies published before (P ≤ 0.0001). The components returning significantly higher scores after publication of PRISMA-A were title (P = 0.024), information from databases (P = 0.026), risk of bias (P ≤ 0.0001), included studies (P ≤ 0.0001), synthesis of results (P ≤ 0.0001), interpretation of results (P = 0.035), financing and conflict of interest (P ≤ 0.0001), and registration (P ≤ 0.0001). These results showed the positive effect of PRISMA-A had on the quality of reporting of orthodontics systematic reviews. Nevertheless, the poor adherence revealed that there is still need for improvement in the quality of abstract reporting.

CONCLUSIONS

The quality of reporting of abstracts of orthodontic systematic reviews and meta-analyses increased after the introduction of PRISMA-A.

Influence of the cranial base flexion on Class I, II and III malocclusions: a systematic review

Objective:

The aim of this study was to perform a systematic review on the morphological characteristics of the skull base (flexion, anterior length and posterior length) and the concomitant development of malocclusions, by comparing differences in dimorphism, ethnicity and age.

Methods:

The articles were selected by means of electronic search on BBO, MEDLINE and LILACS databases from 1966 to 2016. A qualitative evaluation of the methodologies used on the articles was also performed.

Results:

Although the literature on this topic is abundant, only 16 articles were selected for the present systematic review. The cranial base angle itself does not seem to play a significant role in the development of malocclusions. In fact, the cranial base angle is relatively stable at the ages of 5 to 15 years.

Conclusions:

A more obtuse angle at the skull base, in association or not with a greater anterior length of the cranial base, can contribute to the development of Class II division 1 malocclusions. On the other hand, a more acute angle at the skull base can contribute to a more anterior positioning of the mandible and to the development of Class III malocclusions.

Use of recommended search strategies in systematic reviews and the impact of librarian involvement: a cross-sectional survey of recent authors

Background

Previous research looking at published systematic reviews has shown that their search strategies are often suboptimal and that librarian involvement, though recommended, is low. Confidence in the results, however, is limited due to poor reporting of search strategies the published articles.

Objectives

To more accurately measure the use of recommended search methods in systematic reviews, the levels of librarian involvement, and whether librarian involvement predicts the use of recommended methods.

Methods

A survey was sent to all authors of English-language systematic reviews indexed in the Database of Abstracts of Reviews of Effects (DARE) from January 2012 through January 2014. The survey asked about their use of search methods recommended by the Institute of Medicine, Cochrane Collaboration, and the Agency for Healthcare Research and Quality and if and how a librarian was involved in the systematic review. Rates of use of recommended methods and librarian involvement were summarized. The impact of librarian involvement on use of recommended methods was examined using a multivariate logistic regression.

Results

1560 authors completed the survey. Use of recommended search methods ranged widely from 98% for use of keywords to 9% for registration in PROSPERO and were generally higher than in previous studies. 51% of studies involved a librarian, but only 64% acknowledge their assistance. Librarian involvement was significantly associated with the use of 65% of recommended search methods after controlling for other potential predictors. Odds ratios ranged from 1.36 (95% CI 1.06 to 1.75) for including multiple languages to 3.07 (95% CI 2.06 to 4.58) for using controlled vocabulary.

Conclusions

Use of recommended search strategies is higher than previously reported, but many methods are still under-utilized. Librarian involvement predicts the use of most methods, but their involvement is under-reported within the published article.

Librarian co-authors correlated with higher quality reported search strategies in general internal medicine systematic reviews

OBJECTIVES

To determine whether librarian and information specialist authorship was associated with better reported systematic review (SR) search quality.

STUDY DESIGN AND SETTING

SRs from high-impact general internal medicine journals were reviewed for search quality characteristics and reporting quality by independent reviewers using three instruments, including a checklist of Institute of Medicine Recommended Standards for the Search Process and a scored modification of the Peer Review of Electronic Search Strategies instrument.

RESULTS

The level of librarian and information specialist participation was significantly associated with search reproducibility from reported search strategies (Χ(2) = 23.5; P < 0.0001). Librarian co-authored SRs had significantly higher odds of meeting 8 of 13 analyzed search standards than those with no librarian participation and six more than those with mentioned librarian participation. One-way ANOVA showed that differences in total search quality scores between all three groups were statistically significant (F2,267 = 10.1233; P < 0.0001).

CONCLUSION

Problems remain with SR search quality and reporting. SRs with librarian or information specialist co-authors are correlated with significantly higher quality reported search strategies. To minimize bias in SRs, authors and editors could encourage librarian engagement in SRs including authorship as a potential way to help improve documentation of the search strategy.

Epidemiology, quality, and reporting characteristics of systematic reviews and meta-analyses of nursing interventions published in Chinese journals

OBJECTIVES

Systematic reviews (SRs) and meta-analyses (MAs) of nursing interventions have become increasingly popular in China. This review provides the first examination of epidemiological characteristics of these SRs as well as compliance with the Preferred Reporting Items for Systematic Reviews and Meta-analyses and Assessment of Multiple Systematic Reviews guidelines. The purpose of this study was to examine epidemiologic and reporting characteristics as well as the methodologic quality of SRs and MAs of nursing interventions published in Chinese journals.

METHODS

Four Chinese databases were searched (the Chinese Biomedicine Literature Database, Chinese Scientific Journal Full-text Database, Chinese Journal Full-text Database, and Wanfang Database) for SRs and MAs of nursing intervention from inception through June 2013. Data were extracted into Excel (Microsoft, Redmond, WA). The Assessment of Multiple Systematic Reviews and Preferred Reporting Items for Systematic Reviews and Meta-analyses checklists were used to assess methodologic quality and reporting characteristics, respectively.

RESULTS

A total of 144 SRs were identified, most (97.2%) of which used "systematic review" or "meta-analyses" in the titles. None of the reviews had been updated. Nearly half (41%) were written by nurses, and more than half (61%) were reported in specialist journals. The most common conditions studied were endocrine, nutritional and metabolic diseases, and neoplasms. Most (70.8%) reported information about quality assessment, whereas less than half (25%) reported assessing for publication bias. None of the reviews reported a conflict of interest.

CONCLUSIONS

Although many SRs of nursing interventions have been published in Chinese journals, the quality of these reviews is of concern. As a potential key source of information for nurses and nursing administrators, not only were many of these reviews incomplete in the information they provided, but also some results were misleading. Improving the quality of SRs of nursing interventions conducted and published by nurses in China is urgently needed in order to increase the value of these studies.

Comparison of search strategies in systematic reviews of adverse effects to other systematic reviews

BACKGROUND

Research indicates that the methods used to identify data for systematic reviews of adverse effects may need to differ from other systematic reviews.

OBJECTIVES

To compare search methods in systematic reviews of adverse effects with other reviews.

METHODS

The search methodologies in 849 systematic reviews of adverse effects were compared with other reviews.

RESULTS

Poor reporting of search strategies is apparent in both systematic reviews of adverse effects and other types of systematic reviews. Systematic reviews of adverse effects are less likely to restrict their searches to MEDLINE or include only randomised controlled trials (RCTs). The use of other databases is largely dependent on the topic area and the year the review was conducted, with more databases searched in more recent reviews. Adverse effects search terms are used by 72% of reviews and despite recommendations only two reviews report using floating subheadings.

CONCLUSIONS

The poor reporting of search strategies in systematic reviews is universal, as is the dominance of searching MEDLINE. However, reviews of adverse effects are more likely to include a range of study designs (not just RCTs) and search beyond MEDLINE.

Network meta-analyses could be improved by searching more sources and by involving a librarian

OBJECTIVE

Network meta-analyses (NMAs) aim to rank the benefits (or harms) of interventions, based on all available randomized controlled trials. Thus, the identification of relevant data is critical. We assessed the conduct of the literature searches in NMAs.

STUDY DESIGN

Published NMAs were retrieved by searching electronic bibliographic databases and other sources. Two independent reviewers selected studies and five trained reviewers abstracted data regarding literature searches, in duplicate. Search method details were examined using descriptive statistics.

RESULTS

Two hundred forty-nine NMAs were included. Eight used previous systematic reviews to identify primary studies without further searching, and five did not report any literature searches. In the 236 studies that used electronic databases to identify primary studies, the median number of databases was 3 (interquartile range: 3-5). MEDLINE, EMBASE, and Cochrane Central Register of Controlled Trials were the most commonly used databases. The most common supplemental search methods included reference lists of included studies (48%), reference lists of previous systematic reviews (40%), and clinical trial registries (32%). None of these supplemental methods was conducted in more than 50% of the NMAs.

CONCLUSION

Literature searches in NMAs could be improved by searching more sources, and by involving a librarian or information specialist.

Search strategies in systematic reviews in periodontology and implant dentistry

OBJECTIVE

To perform an overview of literature search strategies in systematic reviews (SRs) published in periodontology and implant dentistry.

MATERIALS AND METHODS

Two electronic databases (PubMed and Cochrane Database of SRs) were searched, independently and in duplicate, for SRs with meta-analyses on interventions, with the last search performed on 11 November 2012. Manual searches of the reference lists of included SRs and 10 specialty dental journals were conducted. Methodological issues of the search strategies of included SRs were assessed with Cochrane collaboration guidelines and AMSTAR recommendations. The search strategies employed in Cochrane and paper-based SRs were compared.

RESULTS

A total of 146 SRs with meta-analyses were included, including 19 Cochrane and 127 paper-based SRs. Some issues, such as "the use of keywords," were reported in most of the SRs (86%). Other issues, such as "search of grey literature" and "language restriction," were not fully reported (34% and 50% respectively). The quality of search strategy reporting in Cochrane SRs was better than that of paper-based SRs for seven of the eight criteria assessed.

CONCLUSION

There is room for improving the quality of reporting of search strategies in SRs in periodontology and implant dentistry, particularly in SRs published in paper-based journals.

Some improvements are apparent in identifying adverse effects in systematic reviews from 1994 to 2011

OBJECTIVE

An increasing amount of research and guidelines has been published on search methodology and the reporting of search strategies in systematic reviews. This research assessed whether this has lead to any improvements in the reporting and quality of searching in systematic reviews of adverse effects.

STUDY DESIGN AND SETTING

All records within Cochrane Database of Systematic Reviews and Database of Abstracts of Reviews of Effects were scanned for systematic reviews of adverse effects. Data were then extracted on the methods used for information retrieval in these reviews and a descriptive analysis conducted by publication year.

RESULTS

A total of 849 reviews published from 1994 to 2011 met the inclusion criteria. There has been a significant increase (P<0.001) in the number of adverse effects reviews per year from 1994 (n=5) to 2010 (n=104). Some improvements were apparent, such as an increase in the number of databases searched and fewer date and language restrictions applied. However, there has been an increase in reviews limited to data from randomized controlled trials, whereas the reporting of search strategies could still be improved further, with only 9% (74/849) of the reviews reporting reproducible searches.

CONCLUSION

Some improvements in searching systematic reviews of adverse effects are apparent; however, poor reporting of search strategies remains a great obstacle to readers.

A PRISMA assessment of the reporting quality of systematic reviews in orthodontics

OBJECTIVES

To assess the reporting quality of Cochrane and non-Cochrane systematic reviews (SR) in orthodontics and to compare the reporting quality (PRISMA score) with methodological quality (AMSTAR criteria).

MATERIALS AND METHODS

Systematic reviews (n  =  109) published between January 2000 and July 2011 in five leading orthodontic journals were identified and included. The quality of reporting of the included reviews was assessed by two authors in accordance with the PRISMA guidelines. Each article was assigned a cumulative grade based on fulfillment of the applicable criteria, and an overall percentage score was assigned. Descriptive statistics and simple and multiple linear regression analyses were undertaken.

RESULTS

The mean overall PRISMA score was 64.1% (95% confidence interval [CI], 62%-65%). The quality of reporting was considerably better in reviews published in the Cochrane Database of Systematic Reviews (P < .001) than in non-Cochrane reviews. Both multivariable and univariable analysis indicated that journal of publication and number of authors was significantly associated with the PRISMA score. The association between AMSTAR score and modified PRISMA score was also found to be highly statistically significant.

CONCLUSION

Compliance of orthodontic SRs published in orthodontic journals with PRISMA guidelines was deficient in several areas. The quality of reporting assessed using PRISMA guidelines was significantly better in orthodontic SRs published in the Cochrane Database of Systematic Reviews.

The quality of meta-analyses of genetic association studies: a review with recommendations

Although there has been a rapid rise in the publication of meta-analyses of genetic association studies, little is known about their methodological quality. The authors reviewed the quality of 120 randomly selected genetic meta-analyses published between 2005 and 2007. Data extracted included issues of general relevance and other issues specific to genetic epidemiology. Quality was markedly poorer in the 26% of the meta-analyses that accompanied a report on a primary study. Such meta-analyses were predominantly published in specialist journals, and their quality was positively associated with the impact factor of the journal. Among the meta-analyses that did not accompany a primary study, Human Genome Epidemiology reviews tended to score better than the others, although the comparison was limited by relatively small numbers. Comparison of the overall quality with that of genetic meta-analyses published before 2000 showed improvement in both conduct and reporting. However, the quality of the handling of specific genetic issues remains disappointingly low. For a few key general quality issues, the authors compared their findings with findings in other fields of medicine and found that general quality was similar. On the basis of this review, the authors provide practical recommendations for the conduct and reporting of genetic meta-analyses.

The PRISMA statement for reporting systematic reviews and meta-analyses of studies that evaluate health care interventions: explanation and elaboration

Systematic reviews and meta-analyses are essential to summarize evidence relating to efficacy and safety of health care interventions accurately and reliably. The clarity and transparency of these reports, however, is not optimal. Poor reporting of systematic reviews diminishes their value to clinicians, policy makers, and other users.Since the development of the QUOROM (QUality Of Reporting Of Meta-analysis) Statement--a reporting guideline published in 1999--there have been several conceptual, methodological, and practical advances regarding the conduct and reporting of systematic reviews and meta-analyses. Also, reviews of published systematic reviews have found that key information about these studies is often poorly reported. Realizing these issues, an international group that included experienced authors and methodologists developed PRISMA (Preferred Reporting Items for Systematic reviews and Meta-Analyses) as an evolution of the original QUOROM guideline for systematic reviews and meta-analyses of evaluations of health care interventions.The PRISMA Statement consists of a 27-item checklist and a four-phase flow diagram. The checklist includes items deemed essential for transparent reporting of a systematic review. In this Explanation and Elaboration document, we explain the meaning and rationale for each checklist item. For each item, we include an example of good reporting and, where possible, references to relevant empirical studies and methodological literature. The PRISMA Statement, this document, and the associated Web site (http://www.prisma-statement.org/) should be helpful resources to improve reporting of systematic reviews and meta-analyses.

The PRISMA statement for reporting systematic reviews and meta-analyses of studies that evaluate healthcare interventions: explanation and elaboration

Systematic reviews and meta-analyses are essential to summarise evidence relating to efficacy and safety of healthcare interventions accurately and reliably. The clarity and transparency of these reports, however, are not optimal. Poor reporting of systematic reviews diminishes their value to clinicians, policy makers, and other users. Since the development of the QUOROM (quality of reporting of meta-analysis) statement-a reporting guideline published in 1999-there have been several conceptual, methodological, and practical advances regarding the conduct and reporting of systematic reviews and meta-analyses. Also, reviews of published systematic reviews have found that key information about these studies is often poorly reported. Realising these issues, an international group that included experienced authors and methodologists developed PRISMA (preferred reporting items for systematic reviews and meta-analyses) as an evolution of the original QUOROM guideline for systematic reviews and meta-analyses of evaluations of health care interventions. The PRISMA statement consists of a 27-item checklist and a four-phase flow diagram. The checklist includes items deemed essential for transparent reporting of a systematic review. In this explanation and elaboration document, we explain the meaning and rationale for each checklist item. For each item, we include an example of good reporting and, where possible, references to relevant empirical studies and methodological literature. The PRISMA statement, this document, and the associated website (www.prisma-statement.org/) should be helpful resources to improve reporting of systematic reviews and meta-analyses.

Analysis of the reporting of search strategies in Cochrane systematic reviews

BACKGROUND

The Cochrane Handbook for Systematic Reviews of Interventions provides instructions for documenting a systematic review's electronic database search strategy, listing elements that should be in the description. Complete documentation of the search strategy allows readers to evaluate the search when critically appraising a review's quality.

OBJECTIVE

The research analyzed recently published Cochrane reviews to determine whether instructions for describing electronic database search strategies were being followed.

METHODS

Eighty-three new reviews added to the Cochrane Database of Systematic Reviews in the first quarter of 2006 were selected for analysis. Eighteen were subsequently excluded because their searches were conducted only in the specialized registers of Cochrane review groups. The remaining sixty-five reviews were analyzed for the seven elements of an electronic database search strategy description listed in the Cochrane Handbook, using dual review with consensus.

RESULTS

Of the 65 reviews analyzed, none included all 7 recommended elements. Four reviews (6%) included 6 elements. Thirty-two percent (21/65) included 5 or more elements, with 68% (44/65) including 4 or fewer. Three included only 2 elements. The 65 reviews represented 41 different Cochrane review groups.

CONCLUSION

The instructions from the Cochrane Handbook for reporting search strategies are not being consistently employed by groups producing Cochrane reviews.