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Objective: To evaluate the reporting of abstracts of Cochrane Reviews according to PRISMA-A and to investigate a possible association with the abstract´s length., Methods: This is a retrospective, observational study based on all Cochrane Reviews indexed in Medline (via PubMed) until November 18, 2022. In the second part, a random sample of 440 abstracts was drawn, in which PRISMA-A adherence was assessed by two independent reviewers. Analyses were stratified by the year of publication and the number of words., Results: Overall, the median number of words of the 15,188 included abstracts was 469 (IQR 389-686 words), steadily increasing from 353 words in 2000 to 838 words in 2022, with less than one percent of the abstracts in 2022 having ≤ 300 words (in 2000: 30.7%). Analyses on PRISMA-A adherence in the random sample showed a mean score of 6.1 out of 12 fully reported items. Stratified by year, PRISMA-A adherence increased, with higher word counts in 2000-2010 and 2011-2015, while there was no difference in PRISMA-A adherence by abstract length in 2016-2022., Conclusion: Over the years, abstracts of Cochrane Reviews have become longer, running up to 1000 words. This conflicts with the Cochrane Handbook, which recommends a maximum length of 400 until it was aligned with MECIR in 2019, which has recommended a length of <700 words since 2012 but allows up to 1000 words. It is debatable whether such long abstracts meet the key goals of abstracts of being informative, accurate, appealing, and concise., (© 2023 The Authors. Journal of Evidence-Based Medicine published by Chinese Cochrane Center, West China Hospital of Sichuan University and John Wiley & Sons Australia, Ltd.)

Objectives: The objective of the study was to measure the level of agreement between Cochrane reviews of overlapping randomized controlled trials (RCTs) regarding risk-of-bias (RoB) judgments., Study Design and Setting: On November 5, 2017, the Cochrane Database of Systematic Reviews was searched for Cochrane reviews on tobacco. Reviews that included overlapping RCTs were included. RoB judgments were extracted from RoB tables using automated data scraping with manual verification and adjustments. Agreement between the reviews was calculated using Conger's generalized kappa coefficient (κ) and raw agreement (a)., Results: We included 53 Cochrane reviews of 376 RCTs. For the RoB domain "random sequence generation," the level of agreement between the reviews was substantial with κ = 0.63 (95% confidence interval: 0.56 to 0.71; a = 0.80). There was slight-to-moderate agreement between the reviews regarding the domains "allocation concealment": κ = 0.51 (0.41 to 0.61), a = 0.75; "blinding": κ = 0.19 (0.02 to 0.37), a = 0.52; "blinding of outcome assessment": κ = 0.43 (0.14 to 0.72) a = 0.67; and "incomplete outcome data": κ = 0.15 (-0.03 to 0.32), a = 0.64. For "blinding of participants and personnel" and "selective reporting", κ could not be calculated. The raw agreement was 0.40 and 0.42, respectively., Conclusion: The level of agreement between Cochrane reviews regarding RoB judgments ranged from slight to substantial depending on the RoB domain. Further investigations regarding reasons for variation and interventions to improve agreement are needed., (Copyright © 2019 Elsevier Inc. All rights reserved.)

Background: Overviews of reviews (i.e., overviews) compile information from multiple systematic reviews to provide a single synthesis of relevant evidence for healthcare decision-making. Despite their increasing popularity, there are currently no systematically developed reporting guidelines for overviews. This is problematic because the reporting of published overviews varies considerably and is often substandard. Our objective is to use explicit, systematic, and transparent methods to develop an evidence-based and agreement-based reporting guideline for overviews of reviews of healthcare interventions (PRIOR, Preferred Reporting Items for Overviews of Reviews)., Methods: We will develop the PRIOR reporting guideline in four stages, using established methods for developing reporting guidelines in health research. First, we will establish an international and multidisciplinary expert advisory board that will oversee the conduct of the project and provide methodological support. Second, we will use the results of comprehensive literature reviews to develop a list of prospective checklist items for the reporting guideline. Third, we will use a modified Delphi exercise to achieve a high level of expert agreement on the list of items to be included in the PRIOR reporting guideline. We will identify and recruit a group of up to 100 international experts who will provide input into the guideline in three Delphi rounds: the first two rounds will occur via online survey, and the third round will occur during a smaller (8 to 10 participants) in-person meeting that will use a nominal group technique. Fourth, we will produce and publish the PRIOR reporting guideline., Discussion: A systematically developed reporting guideline for overviews could help to improve the accuracy, completeness, and transparency of overviews. This, in turn, could help maximize the value and impact of overviews by allowing more efficient interpretation and use of their research findings.

Background: A standard or consensus definition of a systematic review does not exist. Therefore, if there is no definition about a systematic review in secondary studies that analyse them or the definition is too broad, inappropriate studies might be included in such evidence synthesis. The aim of this study was to analyse the definition of a systematic review (SR) in health care literature, elements of the definitions that are used and to propose a starting point for an explicit and non-ambiguous SR definition., Methods: We included overviews of systematic reviews (OSRs), meta-epidemiological studies and epidemiology textbooks. We extracted the definitions of SRs, as well as the inclusion and exclusion criteria that could indicate which definition of a SR the authors used. We extracted individual elements of SR definitions, categorised and quantified them., Results: Among the 535 analysed sources of information, 188 (35%) provided a definition of a SR. The most commonly used reference points for the definitions of SRs were Cochrane and the PRISMA statement. We found 188 different elements of SR definitions and divided them into 14 categories. The highest number of SR definition elements was found in categories related to searching (N = 51), analysis/synthesis (N = 23), overall methods (N = 22), quality/bias/appraisal/validity (N = 22) and aim/question (N = 13). The same five categories were also the most commonly used combination of categories in the SR definitions., Conclusion: Currently used definitions of SRs are vague and ambiguous, often using terms such as clear, explicit and systematic, without further elaboration. In this manuscript we propose a more specific definition of a systematic review, with the ultimate aim of motivating the research community to establish a clear and unambiguous definition of this type of research.

Objective: We analyzed patterns of publication of Cochrane review protocols (CRPs)., Study Design and Setting: We analyzed CRPs published in 2010, extracted their characteristics, and analyzed whether they were published by February 2018. We surveyed corresponding authors and Cochrane review groups to analyze reasons for nonpublication of protocols and analyzed factors predicting the time to publication., Results: Of 576 CRPs, 446 (77.4%) were published as a full review and 130 (22.6%) were still unpublished in February 2018; among unpublished, 37 (28.5%) were withdrawn and 93 (71.5%) were still active. The most common authors' reason for abandoning a protocol was a lack of time to work on the review. The median time to publication was 2.78 years (range 0.96 to 8.05). Multivariate analysis showed that factors with the strongest association with shorter time to publication were review being an update and new authors added. Analysis only on methodological variables indicated that the strongest association for a shorter time until publication was found for including only published data., Conclusions: Almost a quarter of CRPs remains unpublished after 8 years. This figure is slightly higher than in a previous analysis 10 years ago. Strategies for enhancing completion of Cochrane reviews should be considered., (Copyright © 2019 Elsevier Inc. All rights reserved.)

Objective: There is a movement from generic quality checklists toward a more domain-based approach in critical appraisal tools. This study aimed to report on a first experience with the newly developed risk of bias in systematic reviews (ROBIS) tool and compare it with A Measurement Tool to Assess Systematic Reviews (AMSTAR), that is, the most common used tool to assess methodological quality of systematic reviews while assessing validity, reliability, and applicability., Study Design and Setting: Validation study with four reviewers based on 16 systematic reviews in the field of occupational health., Results: Interrater reliability (IRR) of all four raters was highest for domain 2 (Fleiss' kappa κ = 0.56) and lowest for domain 4 (κ = 0.04). For ROBIS, median IRR was κ = 0.52 (range 0.13-0.88) for the experienced pair of raters compared to κ = 0.32 (range 0.12-0.76) for the less experienced pair of raters. The percentage of "yes" scores of each review of ROBIS ratings was strongly correlated with the AMSTAR ratings (r s  = 0.76; P = 0.01)., Conclusion: ROBIS has fair reliability and good construct validity to assess the risk of bias in systematic reviews. More validation studies are needed to investigate reliability and applicability, in particular., (Copyright © 2017 Elsevier Inc. All rights reserved.)

Objectives: The aim of the study was to examine the application, design, and analysis characteristics of controlled before-after (CBA) and interrupted time series (ITS) studies and their use in Cochrane reviews., Study Design and Setting: We searched the Cochrane library for reviews including these study designs from May 2012 to March 2015 and purposively selected, where available, two reviews each across 10 prespecified intervention types. We randomly selected two CBA and two ITS studies from each review. Two researchers independently extracted information from the studies and the respective reviews., Results: Sixty-nine reviews considered CBA and ITS studies for inclusion. We analyzed 21 CBA and 16 ITS studies from 11 to 8 reviews, respectively. Cochrane reviews inconsistently defined and labeled CBA and ITS studies. Many studies did not meet the Cochrane definition or the minimum criteria provided by Cochrane Effective Practice and Organisation of Care. The studies present a heterogeneous set of study features and applied a large variety of analyses., Conclusion: While CBA and ITS studies represent important study designs to evaluate the effects of interventions, especially on a population or organizational level, unclear study design features challenge unequivocal classification and appropriate use. We discuss options for more specific definitions and explicit criteria for CBA and ITS studies., (Copyright © 2017 Elsevier Inc. All rights reserved.)

Distinguishing cohort studies from case series is difficult.We propose a conceptualization of cohort studies in systematic reviews of comparative studies. The main aim of this conceptualization is to clarify the distinction between cohort studies and case series. We discuss the potential impact of the proposed conceptualization on the body of evidence and workload.All studies with exposure-based sampling gather multiple exposures (with at least two different exposures or levels of exposure) and enable calculation of relative risks that should be considered cohort studies in systematic reviews, including non-randomized studies. The term "enables/can" means that a predefined analytic comparison is not a prerequisite (i.e., the absolute risks per group and/or a risk ratio are provided). Instead, all studies for which sufficient data are available for reanalysis to compare different exposures (e.g., sufficient data in the publication) are classified as cohort studies.There are possibly large numbers of studies without a comparison for the exposure of interest but that do provide the necessary data to calculate effect measures for a comparison. Consequently, more studies could be included in a systematic review. Therefore, on the one hand, the outlined approach can increase the confidence in effect estimates and the strengths of conclusions. On the other hand, the workload would increase (e.g., additional data extraction and risk of bias assessment, as well as reanalyses).

Background: Inter-rater reliability (IRR) is mainly assessed based on only two reviewers of unknown expertise. The aim of this paper is to examine differences in the IRR of the Assessment of Multiple Systematic Reviews (AMSTAR) and R(evised)-AMSTAR depending on the pair of reviewers., Methods: Five reviewers independently applied AMSTAR and R-AMSTAR to 16 systematic reviews (eight Cochrane reviews and eight non-Cochrane reviews) from the field of occupational health. Responses were dichotomized and reliability measures were calculated by applying Holsti's method (r) and Cohen's kappa (κ) to all potential pairs of reviewers. Given that five reviewers participated in the study, there were ten possible pairs of reviewers., Results: Inter-rater reliability varied for AMSTAR between r = 0.82 and r = 0.98 (median r = 0.88) using Holsti's method and κ = 0.41 and κ = 0.69 (median κ = 0.52) using Cohen's kappa and for R-AMSTAR between r = 0.77 and r = 0.89 (median r = 0.82) and κ = 0.32 and κ = 0.67 (median κ = 0.45) depending on the pair of reviewers. The same pair of reviewers yielded the highest IRR for both instruments. Pairwise Cohen's kappa reliability measures showed a moderate correlation between AMSTAR and R-AMSTAR (Spearman's ρ =0.50). The mean inter-rater reliability for AMSTAR was highest for item 1 (κ = 1.00) and item 5 (κ = 0.78), while lowest values were found for items 3, 8, 9 and 11, which showed only fair agreement., Conclusions: Inter-rater reliability varies widely depending on the pair of reviewers. There may be some shortcomings associated with conducting reliability studies with only two reviewers. Further studies should include additional reviewers and should probably also take account of their level of expertise.

Introduction: The use of search filters (e. g. for study types) facilitates the process of literature searching. Regional limits might be helpful depending on the research question. Regional search filters are already available for some regions, but not for Germany. Our aim is to give an overview of applied search strategies in systematic reviews (SRs) focusing on Germany., Methods: We searched Medline (via Pubmed) applying a focused search strategy to identify SRs focusing on Germany in January 2016. Study selection and data extraction were performed by two reviewers independently. The search strategies with a focus on Germany were analyzed in terms of reasonableness and completeness relying on the Peer Review of Electronic Search Strategies (PRESS) criteria. A narrative evidence synthesis was performed., Results: In total, 36 SRs (13 written in English) were included. 78% were published in 2012 or later. The majority (89%) of SRs utilized at least two different sources for their search with databases and checking references being the most common. 17 SRs did not use any truncations, ten SRs did not restrict their search to Germany, six SRs reported to have searched for German OR Germany. Only ten articles searched for the term Germany (occasionally jointly with the term Deutschland) without any use of an adjective such as German., Discussion: There is a high interest in regionally focused SRs. The identified search strategies revealed a need for improvement. It would be helpful to develop a regional search filter for Germany that is able to identify studies performed in Germany., (Copyright © 2016. Published by Elsevier GmbH.)

Objective: Some authors of Cochrane overviews have also (co-)authored one or more of the underlying reviews. We examined the extent of dual (co-)authorship in Cochrane overviews, how it is dealt with, and whether the issue is raised in protocols., Study Design: The Cochrane Library was searched for overviews and protocols for overviews in September 2015. Data on dual (co-)authorship were extracted for each review into standard spreadsheets by one author and checked for accuracy by a second., Results: Twenty overviews and 25 protocols were identified. The overviews included a median of 10 reviews (interquartile range [IQR]: 6-18.5). In 18/20 overviews (90%), at least one of the included reviews was affected by dual (co-)authorship. A median of 5 (IQR, 2.5-7) reviews per overview was affected by dual (co-)authorship. In 8/18 (44%) overviews with dual (co-)authorship, quality assessment was conducted independently. In 7/25 (28%) protocols, dual (co-)authorship was mentioned., Conclusion: Potential biases arising from dual (co-)authorship are often neglected in Cochrane overviews. We argue that authors of Cochrane overviews and Review Groups should pay more attention to the issue, to avoid bias and preserve the good reputation that Cochrane overviews will typically deserve., (Copyright © 2016 Elsevier Inc. All rights reserved.)

Background: Evidence syntheses, and in particular systematic reviews (SRs), have become one of the cornerstones of evidence-based health care. The Assessment of Multiple Systematic Reviews (AMSTAR) tool has become the most widely used tool for investigating the methodological quality of SRs and is currently undergoing revision. The objective of this paper is to present insights, challenges and potential solutions from the point of view of a group of assessors, while referring to earlier methodological discussions and debates with respect to AMSTAR., Discussion: One major drawback of AMSTAR is that it relies heavily on reporting quality rather than on methodological quality. This can be found in several items. Furthermore, it should be acknowledged that there are now new methods and procedures that did not exist when AMSTAR was developed. For example, the note to item 1 should now refer to the International Prospective Register of Ongoing Systematic Reviews (PROSPERO). Furthermore, item 3 should consider the definition of hand-searching, as the process of reviewing conference proceedings using the search function (e.g. in Microsoft Word or in a PDF file) does not meet the definition set out by the Cochrane Collaboration. Moreover, methods for assessing the quality of the body of evidence have evolved since AMSTAR was developed and should be incorporated into a revised AMSTAR tool. Potential solutions are presented for each AMSTAR item with the aim of allowing a more thorough assessment of SRs. As the AMSTAR tool is currently undergoing further development, our paper hopes to add to preceding discussions and papers regarding this tool and stimulate further discussion.

Objectives: To summarize all available evidence on measurement properties in terms of reliability, validity, and feasibility of the Assessment of Multiple Systematic Reviews (AMSTAR) tool, including R(evised)-AMSTAR., Study Design and Setting: MEDLINE, EMBASE, Psycinfo, and CINAHL were searched for studies containing information on measurement properties of the tools in October 2013. We extracted data on study characteristics and measurement properties. These data were analyzed following measurement criteria., Results: We included 13 studies, four of them were labeled as validation studies. Nine articles dealt with AMSTAR, two articles dealt with R-AMSTAR, and one article dealt with both instruments. In terms of interrater reliability, most items showed a substantial agreement (>0.6). The median intraclass correlation coefficient (ICC) for the overall score of AMSTAR was 0.83 (range 0.60-0.98), indicating a high agreement. In terms of validity, ICCs were very high with all but one ICC lower than 0.8 when the AMSTAR score was compared with scores from other tools. Scoring AMSTAR takes between 10 and 20 minutes., Conclusion: AMSTAR seems to be reliable and valid. Further investigations for systematic reviews of other study designs than randomized controlled trials are needed. R-AMSTAR should be further investigated as evidence for its use is limited and its measurement properties have not been studied sufficiently. In general, test-retest reliability should be investigated in future studies., (Copyright © 2015 Elsevier Inc. All rights reserved.)

Background and Objective: As systematic reviews may run out of date, it might be necessary to update them. Out-of-date reviews may jeopardize the comparability when used in the context of overviews (review of reviews)., Methods: Seven electronic databases were searched for overviews up to November 2012. We first aimed to analyze whether the authors of overviews additionally searched for primary studies or alternatively explained why they did not. Second, we sought to analyze the actual publication lag (publication date of the overview - publication date of the review) in overviews and to develop recommendations for authors of overviews., Results: We included 147 overviews. The mean publication lag in overviews was more than 5 years. A median of 36% of the reviews were published more than 6 years ago. Only one in four reviews considered up-to-dateness. The methods for updating reviews were heterogeneous. We found no overview that systematically investigated whether an update was necessary., Conclusion: The issue of up-to-dateness when conducting overviews seems to be neglected by most authors of overviews. Authors should assess the quality of evidence, based on their included reviews first., (Copyright © 2014 Elsevier Inc. All rights reserved.)

Introduction: The quality of systematic reviews of health economic evaluations (SR-HE) is often limited because of methodological shortcomings. One reason for this poor quality is that there are no established standards for the preparation of SR-HE. The objective of this study is to compare existing methods and suggest best practices for the preparation of SR-HE., Methods: To identify the relevant methodological literature on SR-HE, a systematic literature search was performed in Embase, Medline, the National Health System Economic Evaluation Database, the Health Technology Assessment Database, and the Cochrane methodology register, and webpages of international health technology assessment agencies were searched. The study selection was performed independently by 2 reviewers. Data were extracted by one reviewer and verified by a second reviewer. On the basis of the overlaps in the recommendations for the methods of SR-HE in the included papers, suggestions for best practices for the preparation of SR-HE were developed., Results: Nineteen relevant publications were identified. The recommendations within them often differed. However, for most process steps there was some overlap between recommendations for the methods of preparation. The overlaps were taken as basis on which to develop suggestions for the following process steps of preparation: defining the research question, developing eligibility criteria, conducting a literature search, selecting studies, assessing the methodological study quality, assessing transferability, and synthesizing data., Discussion: The differences in the proposed recommendations are not always explainable by the focus on certain evaluation types, target audiences, or integration in the decision process. Currently, there seem to be no standard methods for the preparation of SR-HE. The suggestions presented here can contribute to the harmonization of methods for the preparation of SR-HE., (© The Author(s) 2014.)

Background: There is a lack of an instrument to evaluate systematic reviews of non-randomized studies in epidemiological research. The Assessment of Multiple Systematic Reviews (AMSTAR) is widely used to evaluate the scientific quality of systematic reviews, but it has not been validated for SRs of non-randomized studies. The objective of this paper is to report our experience in applying AMSTAR to systematic reviews of non-randomized studies in terms of applicability, reliability and feasibility. Thus, we applied AMSTAR to a recently published review of 32 systematic reviews of non-randomized studies investigating the hospital volume-outcome relationship in surgery., Results: The inter-rater reliability was high (0.76), albeit items 8 (scientific quality used in formulating conclusions), 9 (appropriate method to combine studies), and 11 (conflicts of interest) scored moderate (≤0.58). However, there was a high heterogeneity between the two pairs of reviewers. In terms of feasibility, AMSTAR proved easy to apply to systematic reviews of non-randomized studies, each review taking 5-10 minutes to complete. We faced problems in applying three items, mainly related to scientific quality of the included studies., Conclusions: AMSTAR showed good psychometric properties, comparable to prior findings in systematic reviews of randomized controlled trials. AMSTAR can be applied to systematic reviews of non-randomized studies, although there are some item specific issues users should be aware of. Revisions and extensions of AMSTAR might be helpful.

Objectives: Overviews search for reviews rather than for primary studies. They might have the potential to support decision making within a shorter time frame by reducing production time. We aimed to summarize available instructions for authors intending to conduct overviews as well as the currently applied methodology of overviews in international Health Technology Assessment (HTA) agencies., Methods: We identified 127 HTA agencies and scanned their websites for methodological handbooks as well as published overviews as HTA reports. Additionally, we contacted HTA agencies by e-mail to retrieve possible unidentified handbooks or other related sources., Results: In total, eight HTA agencies providing methodological support were found. Thirteen HTA agencies were found to have produced overviews since 2007, but only six of them published more than four overviews. Overviews were mostly employed in HTA products related to rapid assessment. Additional searches for primary studies published after the last review are often mentioned in order to update results., Conclusions: Although the interest in overviews is rising, little methodological guidance for the conduct of overviews is provided by HTA agencies. Overviews are of special interest in the context of rapid assessments to support policy-making within a short time frame. Therefore, empirical work on overviews needs to be extended. National strategies and experience should be disclosed and discussed., (Copyright © 2013 John Wiley & Sons, Ltd.)

Objective: The question whether the choice of a critical appraisal tool has an impact on the result of the evidence synthesis in systematic reviews has been neglected by research. This is also true for psychometric properties of critical appraisal tools. The objective of the study is to exemplify that in the context of overviews (reviews of reviews)., Methods: Based on a published overview investigating the hospital volume-outcome relationship in surgery, 32 therein included systematic reviews were independently evaluated with four critical appraisal tools by two reviewers. We rated the relationship on a five-point rating scale using qualitative evidence synthesis. Measures of reliability and correlation coefficients were calculated., Results: The result of the evidence synthesis was not dependent on the choice of a critical appraisal tool. Inter-rater reliability differed depending on the tool, Cohens Kappa ranging from 0.47 to 0.76. There was a high heterogeneity between the two pairs of reviewers., Conclusion: The choice of a critical appraisal tool has no impact on the result of the evidence synthesis, despite differences in the covered components by each CAT. Further studies should concentrate on investigating psychometric properties and the impact of choice of CATs on the evidence synthesis in other contexts. The high heterogeneity between the two pairs of reviewers, all of them experienced in appraising systematic reviews, indicates a degree of interpretability in the items., (© 2014 Chinese Cochrane Center, West China Hospital of Sichuan University and Wiley Publishing Asia Pty Ltd.)

Objectives: The objective of this study was to determine if the authors mention overlapping reviews in overviews (reviews of reviews). In addition, we aimed to calculate the actual overlap in published overviews using newly introduced, validated measures., Study Design and Settings: We systematically searched for overviews from 2009 to 2011. Reviews included in the overviews were obtained. Tables (review×primary publication) were generated for each overview. The first occurrence of a primary publication is defined as the index publication. We calculated the "corrected covered area" (CCA) as a measure of overlap by dividing the frequency of repeated occurrences of the index publication in other reviews by the product of index publications and reviews, reduced by the number of index publications. Subgroup analyses were performed to investigate further differences in the overviews., Results: Only 32 of 60 overviews mentioned overlaps. The median CCA was 4.0. Validation of the CCA and other overlap measures was in accordance with our predefined hypotheses. The degree of overlap tended to be higher in health technology assessment reports than in journal publications and was higher with increasing numbers of publications., Conclusions: Overlaps must be reported in well-conducted overviews, and this can comprehensively be accomplished using the CCA method., (Copyright © 2014 Elsevier Inc. All rights reserved.)

The increase in scientific literature has led reviewers to conduct overviews, hereby creating a new publication type. Overviews of reviews may have several advantages. For example, they can be conducted in a shorter time frame, they offer the opportunity of providing decision makers with a broader summary of the evidence, allowing comparison of multiple treatments, and they can be helpful in investigating discordant findings from multiple systematic reviews. However, there are some specific characteristics concerning methodology in conducting overviews. Questions that arise are how to deal with overlapping reviews, how the quality of the included reviews should be assessed, how discordant results should be dealt with, whether and how additional searches for current primary studies should be conducted. Overviews of reviews often lack methodological rigour. Methodological standards and reporting guidelines for overviews are needed to improve the quality of this new publication type., (Copyright © 2013. Published by Elsevier GmbH.)

Objective: To examine published overviews of systematic reviews in terms of descriptive and methodological characteristics., Study Design and Setting: MEDLINE, Database of Abstracts of Reviews of Effects, the Cochrane Database of Systematic Reviews, and several Health Technology Assessment databases were searched for overviews of reviews up to February 2012. We extracted data from the methods and results sections of the included overviews. These data were analyzed descriptively as frequencies or medians and interquartile ranges., Results: We included 126 overviews of reviews. According to our sample, publication rates for overviews have risen in the last decade. The quality of the included reviews was systematically appraised in 64% of the overviews. The most commonly used assessment tools were the Overview Quality Assessment Questionnaire (26%), Assessment of Multiple Systematic Reviews (11%), and Preferred Reporting Items for Systematic Reviews and Meta-Analyses (5%). Only three of 18 overviews restricted to Cochrane reviews in our sample performed a quality assessment. Strategies to deal with discordant reviews were reported in 5% of the overviews. Searches for additional primary studies were conducted in 5% of the overviews., Conclusion: Overviews of reviews often lack methodological rigor. Methodological standards and reporting guidelines for overviews are needed to improve the quality of this new publication type., (Copyright © 2012 Elsevier Inc. All rights reserved.)