How many cochrane reviews

One of these discusses the introduction of reviews of diagnostic test accuracy rather than the effects on health outcomes of particular tests , which have started to pave the way for Cochrane to include other types of systematic review alongside its more traditional reviews of the effects of interventions.

Across The Cochrane Collaboration, other specific methods networks are examining the appraisal and reporting of adverse effects, the use of non-randomized designs including the assessment of bias in these studies, the development of methods to prioritize and update reviews, and the consideration of equity in both the conduct and the interpretation of reviews.

The ongoing drive for The Cochrane Collaboration is to ensure that it produces high quality, relevant and up to date systematic reviews. In keeping with the need to continue to improve the quality of reporting [ 20 — 23 ], The Cochrane Collaboration has produced a set of standards.

These standards [ 24 ] cover the conduct and reporting of reviews, including the reporting of protocols and the updating of reviews. The Cochrane Collaboration is committed to pioneering research that will lead to further improvements in the methods used for Cochrane Reviews.

As an example, the Cochrane Methods Innovation Fund has supported six methods related projects since A fundamental feature of Cochrane Reviews since the start of the Collaboration has been the requirement to update them periodically. Twenty years on, methodology research is seeking to establish the longevity of the clinical relevance of Cochrane Reviews, taking account of changes in methodology as well as additional evidence.

This will help to ensure that the quality of each Cochrane Review improves alongside the incorporation of more recent studies [ 25 ]. Future research is needed to determine the feasibility and efficiency of updating and prioritization strategies, including statistical techniques [ 27 , 28 ], so that the necessary guidance can be prepared. The need for systematic reviews to inform decision making in health and social care will remain into the foreseeable future [ 29 ].

This highlights the ongoing importance of the collaborative effort of The Cochrane Collaboration amongst others to continue to use sound methods to aggregate the ever-increasing number of new studies.

Technological as well as methodological progress is key to advancing the aggregation and dissemination of systematic review evidence [ 30 ]. Some challenges for systematic reviews arise from successes in improving access to the potentially eligible studies including prospective registration of randomized trials [ 31 ], the ongoing push for greater availability of published as well as unpublished study reports [ 32 ] and the need to update reviews to inform and interpret new research will require robust methods, and resources.

The capacity to identify and appraise the underlying research and to systematically synthesize the evidence will continue to be challenging for organizations such as The Cochrane Collaboration. This article outlined the breadth and diversity of systematic review methods that are being incorporated in Cochrane Reviews. These, and other, systematic reviews need to encompass a range of evidential data [ 33 ], to determine treatment effectiveness and to explain, inform, contextualize and triangulate the findings.

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Oxman A: The Cochrane Collaboration in the 21 st century: ten challenges and one reason why they must be met. Chapter Google Scholar. Int J Surg. Ann Intern Med. Institute of Medicine: Standards for Systematic Reviews. PLoS One. Mallett S, Clarke M: How many Cochrane Reviews are needed to cover existing evidence on the effects of healthcare interventions? Tovey D: Impact of Cochrane Reviews [editorial]. PLoS Med.

Book Google Scholar. Abbott A: Chaos of Disciplines. Download references. You can also search for this author in PubMed Google Scholar. Correspondence to Jackie Chandler. JC conceived the paper as part of an outline for this Systematic Reviews series and developed the initial draft.

SH commented on and edited subsequent drafts of the manuscript. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Competing interests: PM is the author of several empty reviews published by the Cochrane Collaboration.

The Cochrane Library is the largest and perhaps best recognized global collection of health care evidence, currently hosting more than 4, systematic reviews in its Cochrane Database of Systematic Reviews CDSR. However, it has been reported that clinicians find Cochrane reviews of limited relevance to practice decisions.

For example, one study found that while Cochrane reviews are highly regarded for their quality, they are used less than other sources for clinical decision-making because of their emphasis on methodology and rigor rather than on clinical relevance [1].

It is not Cochrane's policy to provide guidelines for practice or policy decisions [2]. Little is known about the incidence, prevalence or variation in reporting of such reviews [3].

The little that has been written about them suggests that the reporting of implications for practice may sustain a risk for bias.

With no studies meeting criteria for inclusion, these empty reviews may appear to: 1 offer no conclusions, 2 offer conclusions based on referenced excluded studies, 3 offer conclusions based on other evidence, or 4 offer conclusions not based on evidence. Thus, empty reviews may contribute to what appears to be generalized disappointment with The CDSR among some clinicians and policymakers [1] , [4]. In examining the literature concerning empty reviews, we offer the following summary of the core issues.

First, empty reviews may relate to an area of study which is very new. Cooper asserts that research syntheses should concern topics for which there is already a body of evidence [4]. Where it is important to identify new interventions and gaps in knowledge, systematic reviews provide direction for targeted research and in some countries, may be required as part of large grant applications for trials.

Second, in some circumstances, reviews may focus on questions that are highly specific. For example, they may restrict the population by age, context, diagnostic criteria, or intervention criteria.

In the case that studies meeting these specified criteria have not been conducted, there are no includable studies. Third, many empty reviews may be the result of overly stringent methodological inclusion criteria imposed in the interest of higher quality evidence.

These criteria may involve study selection based on specific designs, outcome measures, or comparison conditions which may not be available in existing primary studies. The issue of empty reviews was introduced to the literature in by Lang and colleagues, who suggested that guidelines were needed for reporting of empty reviews in order to prevent reviewers from deriving unsubstantiated implications for practice, or from simply concluding that no eligible studies were found [3].

Lang et al. In response, Green et al. The Cochrane Handbook for Systematic Reviews of Interventions sets policy and provides specific guidance for the reporting of Cochrane systematic reviews but does not yet provide specific guidance for the reporting of empty reviews [2]. As a result, the reporting of empty reviews may be inconsistent. The objectives of the present study were to provide a description of empty reviews and their general characteristics in The CDSR and across topic areas as defined by Cochrane Review Groups.

To explore the extent to which empty reviews are reported in The CDSR , we first identified all reviews without included studies and examined their frequency and proportion overall as well as within Cochrane Review Groups.

Second, to examine the persistence of empty reviews, we analyzed time since original publication of identified reviews. Third, to assess the level of existing, but non-includable, research related to topics of empty reviews, we examined the number of excluded studies reported by each of these reviews across The CDSR and within Cochrane Review Groups. Finally, to assess the possibility of future updating with eligible studies, we examined time since last update of these reviews as well as numbers of reported on-going studies and studies awaiting assessment.

In this way, we hoped to establish whether the prevalence and general characteristics of empty reviews varied systematically across Cochrane Review Groups. We assumed that inconsistencies in prevalence and characteristics across Cochrane Review Groups might suggest the necessity of general guidelines for the reporting of empty reviews in The CDSR. The Cochrane Collaboration Information Management System Archie was used to identify any Cochrane systematic reviews through December that contained no included studies.

These reviews were verified as empty by two authors. Remaining reviews from January to August 15, were identified through hand search of The CDSR by one author and verified by a second author.

PDF versions of empty reviews were downloaded and data extracted from relevant sections of reviews by one author and verified by a second author. Age of reviews was calculated in years between the original publication year and Time since last update was calculated in years between the date reported in the history section of each review and August 15, Data calculations were performed by one author and verified by a second author.

Any disagreements between the two authors were resolved by discussion. Differences across Cochrane Review Groups were detected by visual analysis. Forty-five In contrast, several Cochrane Review Groups sustained higher numbers of these empty reviews, although raw numbers of empty reviews can only be understood in the context of the total numbers of reviews supported by these groups.

For example, the Pregnancy and Childbirth Group listed the largest number of empty reviews with 35, but this number represented only 8. Table 1 displays the total number of systematic reviews, number of empty reviews, and percentage of reviews which were empty for each of the 53 Cochrane Review Groups on August 15, Distribution of empty reviews varied considerably across groups.

Figure 1 presents the distribution of empty reviews by date of original publication. Twenty of these reviews have remained empty from the s and from before One hundred forty-five Cochrane Handbook for systematic reviews of interventions. Search PubMed Greenhalgh T. Outside the box: Why are Cochrane reviews so boring? Br J Gen Pract ;62 Readability of Cochrane Breast Cancer Group plain language summaries.

Abstracts of the 21st Cochrane Colloquium. Guidelines and systematic reviews: Sizing up guidelines in general practice. Aust Fam Physician ;46 6 — Search PubMed van Driel M. Growing research — Involving students in Cochrane reviews. Aust Fam Physician ;40 10 Onychomycosis tinea of the nails. In: eTG complete [Internet]. Melbourne: Therapeutic Guidelines Limited, Search PubMed Cochrane Collaboration. What is Cochrane evidence and how can it help you? London: Cochrane Collaboration, Available at www.

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JAMA ; 20 — Improving the uptake of systematic reviews: A systematic review of intervention effectiveness and relevance. BMJ Open ;4 10 :e Summary-of-findings tables in Cochrane reviews improved understanding and rapid retrieval of key information.

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