Does Bradford's Law of Scattering predict the size of the literature in Cochrane Reviews?
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ABSTRACT:
SUBMITTER: Nash-Stewart CE
PROVIDER: S-EPMC3324807 | biostudies-literature | 2012 Apr
REPOSITORIES: biostudies-literature
Publications
Does Bradford's Law of Scattering predict the size of the literature in Cochrane Reviews?
Nash-Stewart Charlotte E CE Kruesi Lisa M LM Del Mar Chris B CB
Journal of the Medical Library Association : JMLA 20120401 2
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Project description:In 1996, shortly after the founding of The Cochrane Collaboration, leading figures in test evaluation research established a Methods Group to focus on the relatively new and rapidly evolving methods for the systematic review of studies of diagnostic tests. Seven years later, the Collaboration decided it was time to develop a publication format and methodology for Diagnostic Test Accuracy (DTA) reviews, as well as the software needed to implement these reviews in The Cochrane Library. A meeting hosted by the German Cochrane Centre in 2004 brought together key methodologists in the area, many of whom became closely involved in the subsequent development of the methodological framework for DTA reviews. DTA reviews first appeared in The Cochrane Library in 2008 and are now an integral part of the work of the Collaboration.
| S-EPMC3851548 | biostudies-literature
Project description:BackgroundMost meta-analyses include data from one or more small studies that, individually, do not have power to detect an intervention effect. The relative influence of adequately powered and underpowered studies in published meta-analyses has not previously been explored. We examine the distribution of power available in studies within meta-analyses published in Cochrane reviews, and investigate the impact of underpowered studies on meta-analysis results.Methods and findingsFor 14,886 meta-analyses of binary outcomes from 1,991 Cochrane reviews, we calculated power per study within each meta-analysis. We defined adequate power as ?50% power to detect a 30% relative risk reduction. In a subset of 1,107 meta-analyses including 5 or more studies with at least two adequately powered and at least one underpowered, results were compared with and without underpowered studies. In 10,492 (70%) of 14,886 meta-analyses, all included studies were underpowered; only 2,588 (17%) included at least two adequately powered studies. 34% of the meta-analyses themselves were adequately powered. The median of summary relative risks was 0.75 across all meta-analyses (inter-quartile range 0.55 to 0.89). In the subset examined, odds ratios in underpowered studies were 15% lower (95% CI 11% to 18%, P<0.0001) than in adequately powered studies, in meta-analyses of controlled pharmacological trials; and 12% lower (95% CI 7% to 17%, P<0.0001) in meta-analyses of controlled non-pharmacological trials. The standard error of the intervention effect increased by a median of 11% (inter-quartile range -1% to 35%) when underpowered studies were omitted; and between-study heterogeneity tended to decrease.ConclusionsWhen at least two adequately powered studies are available in meta-analyses reported by Cochrane reviews, underpowered studies often contribute little information, and could be left out if a rapid review of the evidence is required. However, underpowered studies made up the entirety of the evidence in most Cochrane reviews.
| S-EPMC3609745 | biostudies-literature
Project description:BACKGROUND: Eczema is the most common inflammatory skin disease of childhood, characterized by an itchy red rash that usually involves the face and skin folds. There is currently no curative treatment for eczema, so the reduction of eczema incidence through disease prevention is a desirable goal. Potential interventions for preventing eczema include exclusive breastfeeding, hydrolysed protein formulas and soy formulas when bottle feeding, maternal antigen avoidance, omega oil supplementation, prebiotics and probiotics. OBJECTIVES: This overview of reviews aims to present the current body of data from Cochrane and non-Cochrane reviews to provide the most up-to-date evidence on the efficacy and safety of interventions to prevent eczema in infants and children at different risk levels for developing allergic disease. METHODS: Our pool of Cochrane and non-Cochrane reviews came from the 2010 United Kingdom National Health Service (NHS) Evidence Skin Disorders Annual Evidence Updates Mapping Exercise on Atopic Eczema. This group used a comprehensive search strategy last conducted in August 2010 to identify all systematic reviews on eczema prevention. We identified all reviews that met our pre-specified inclusion criteria, and data were extracted, analysed, compiled into tables and synthesized using quantitative and qualitative methods. MAIN RESULTS: Seven systematic reviews containing 39 relevant trials with 11 897 participants were included in this overview. Overall, there was no clear evidence that any of the main interventions reviewed reduced eczema incidence. In subgroup analyses of infants at high risk of allergic disease, an observational study found that exclusive breastfeeding for at least six months compared with introduction of solids at three to six months decreased the incidence of eczema by 60% (risk ratio (RR): 0.40; 95% confidence interval (CI): 0.21, 0.78), and a randomized controlled trial found that prebiotics compared with no prebiotics decreased incidence by 58% (RR: 0.42; 95% CI: 0.21, 0.84). However, each of these findings was based on the results of a single small trial, and no intervention reduced eczema incidence beyond the first two years of life. Although we pre-specified incidence of atopic eczema (i.e. eczema associated with immunoglobulin E (IgE) sensitization) as a primary outcome, data on whether participants diagnosed with eczema were truly atopic were largely lacking from systematic reviews. Similarly, data on atopy, measured using skin prick tests or specific IgE tests to allergens, were not reported in many reviews. No interventions were found to decrease atopy when reported. Adverse events data were generally lacking, but data from a trial of probiotics versus no probiotics showed significantly more spitting up in the first one (RR: 1.88; 95% CI: 1.03, 3.45) and two (RR: 1.69; 95% CI: 1.02, 2.80) months of life, but no overall increase in risk of gastrointestinal symptoms in the first year. AUTHORS#ENTITYSTARTX02019; CONCLUSIONS: Although there is currently no clear evidence showing that any of the interventions examined in this overview prevent eczema in participants not selected for risk of allergic disease, there is some evidence that exclusive breastfeeding for at least six months and prebiotics might reduce eczema incidence in high-risk participants. However, these conclusions are based on limited evidence with methodological shortcomings. Future research on prevention of eczema is needed and should examine different types of hydrolysed formulas, prebiotics and probiotics, as well as enhancement of the skin barrier and other novel approaches in infants at different risk levels for developing allergic disease.
| S-EPMC3399595 | biostudies-other
Project description:BackgroundSystematic reviews with meta-analyses often contain many statistical tests. This multiplicity may increase the risk of type I error. Few attempts have been made to address the problem of statistical multiplicity in systematic reviews. Before the implications are properly considered, the size of the issue deserves clarification. Because of the emphasis on bias evaluation and because of the editorial processes involved, Cochrane reviews may contain more multiplicity than their non-Cochrane counterparts. This study measured the quantity of statistical multiplicity present in a population of systematic reviews and aimed to assess whether this quantity is different in Cochrane and non-Cochrane reviews.Methods/principal findingsWe selected all the systematic reviews published by the Cochrane Anaesthesia Review Group containing a meta-analysis and matched them with comparable non-Cochrane reviews. We counted the number of statistical tests done in each systematic review. The median number of tests overall was 10 (interquartile range (IQR) 6 to 18). The median was 12 in Cochrane and 8 in non-Cochrane reviews (difference in medians 4 (95% confidence interval (CI) 2.0-19.0). The proportion that used an assessment of risk of bias as a reason for doing extra analyses was 42% in Cochrane and 28% in non-Cochrane reviews (difference in proportions 14% (95% CI -8 to 36). The issue of multiplicity was addressed in 6% of all the reviews.Conclusion/significanceStatistical multiplicity in systematic reviews requires attention. We found more multiplicity in Cochrane reviews than in non-Cochrane reviews. Many of the reasons for the increase in multiplicity may well represent improved methodological approaches and greater transparency, but multiplicity may also cause an increased risk of spurious conclusions. Few systematic reviews, whether Cochrane or non-Cochrane, address the issue of multiplicity.
| S-EPMC3229598 | biostudies-literature
Project description:BackgroundResearch turnover in the HIV field is rapid, and as a result, maintaining high-quality, up-to-date, and relevant systematic reviews is a challenge. One approach is to frequently update published reviews.MethodsWe evaluated the methods and relevance of all HIV systematic reviews and protocols published in the Cochrane Library over a 16-year period (2000-2016) to determine the need to update published reviews or complete of reviews in progress.ResultsOf 148 published reviews and protocols, 129 (87%) were identified as not for updating or progression to publication, mostly due to research questions which were either entirely outdated or addressed questions in an outdated manner (N = 89; 60%); this was anticipated for older reviews, but was found also to be the case for recent publications. Some research questions were also inadequately conceptualized, particularly when complex pragmatic trials or behavioral interventions were included.ConclusionsWe suggest that authors clearly characterize interventions and synthesis approaches in their review protocols. In research fields, such as HIV, where questions change frequently, systematic reviews and protocols should be regularly re-evaluated to ensure relevance to current questions. This process of re-evaluation should be incorporated into the methods of living systematic reviews.
| S-EPMC6366015 | biostudies-literature
Project description: Not available
| S-EPMC9715299 | biostudies-literature
Project description:ObjectivesTo develop methods guidance to support the conduct of rapid reviews (RRs) produced within Cochrane and beyond, in response to requests for timely evidence syntheses for decision-making purposes including urgent health issues of high priority.Study design and settingInterim recommendations were informed by a scoping review of the underlying evidence, primary methods studies conducted, and a survey sent to 119 representatives from 20 Cochrane entities, who were asked to rate and rank RR methods across stages of review conduct. Discussions among those with expertise in RR methods further informed the list of recommendations with accompanying rationales provided.ResultsBased on survey results from 63 respondents (53% response rate), 26 RR methods recommendations are presented for which there was a high or moderate level of agreement or scored highest in the absence of such agreement. Where possible, how recommendations align with Cochrane methods guidance for systematic reviews is highlighted.ConclusionThe Cochrane Rapid Reviews Methods Group offers new, interim guidance to support the conduct of RRs. Because best practice is limited by the lack of currently available evidence for some RR methods shortcuts taken, this guidance will need to be updated as additional abbreviated methods are evaluated.
| S-EPMC7557165 | biostudies-literature
Project description:Systematic reviews (SRs) are considered an important tool for decision-making. There has been no recent comprehensive identification or description of child-relevant SRs. A description of existing child-relevant SRs would help to identify the extent of available child-relevant evidence available in SRs and gaps in the evidence base where SRs are required. The objective of this study was to describe child-relevant SRs from the Cochrane Database of Systematic Reviews (CDSR, Issue 2, 2009).SRs were assessed for relevance using pre-defined criteria. Data were extracted and entered into an electronic form. Univariate analyses were performed to describe the SRs overall and by topic area.The search yielded 1666 SRs; 793 met the inclusion criteria. 38% of SRs were last assessed as up-to-date prior to 2007. Corresponding authors were most often from the UK (41%). Most SRs (59%) examined pharmacological interventions. 53% had at least one external source of funding. SRs included a median of 7 studies (IQR 3, 15) and 679 participants (IQR 179, 2833). Of all studies, 48% included only children, and 27% only adults. 94% of studies were published in peer-reviewed journals. Primary outcomes were specified in 72% of SRs. Allocation concealment and the Jadad scale were used in 97% and 25% of SRs, respectively. Adults and children were analyzed separately in 12% of SRs and as a subgroup analysis in 14%. Publication bias was assessed in only 14% of SRs. A meta-analysis was conducted in 68% of SRs with a median of 5 trials (IQR 3, 9) each. Variations in these characteristics were observed across topic areas.We described the methodological characteristics and rigour of child-relevant reviews in the CDSR. Many SRs are not up-to-date according to Cochrane criteria. Our study describes variation in conduct and reporting across SRs and reveals clinicians' ability to access child-specific data.
| S-EPMC2881081 | biostudies-other
Project description:ObjectiveTo assess the quality of Cochrane reviews.DesignTen methodologists affiliated with the Cochrane Collaboration independently examined, in a semistructured way, the quality of reviews first published in 1998. Each review was assessed by two people; if one of them noted any major problems, they agreed on a common assessment. Predominant types of problem were categorised.SettingCyberspace collaboration coordinated from the Nordic Cochrane Centre.StudiesAll 53 reviews first published in issue 4 of the Cochrane Library in 1998.Main outcome measureProportion of reviews with various types of major problem.ResultsNo problems or only minor ones were found in most reviews. Major problems were identified in 15 reviews (29%). The evidence did not fully support the conclusion in nine reviews (17%), the conduct or reporting was unsatisfactory in 12 reviews (23%), and stylistic problems were identified in 12 reviews (23%). The problematic conclusions all gave too favourable a picture of the experimental intervention.ConclusionsCochrane reviews have previously been shown to be of higher quality and less biased on average than other systematic reviews, but improvement is always possible. The Cochrane Collaboration has taken steps to improve editorial processes and the quality of its reviews. Meanwhile, the Cochrane Library remains a key source of evidence about the effects of healthcare interventions. Its users should interpret reviews cautiously, particularly those with conclusions favouring experimental interventions and those with many typographical errors.
| S-EPMC57800 | biostudies-literature
Project description:IntroductionEvidence of different smoking cessation interventions varies and has been assessed in many Cochrane reviews. We conducted an overview of these Cochrane reviews to summarize the effects of current interventions for smoking cessation.MethodsNine databases were searched from their inception to October 2024, with no restrictions on language. Two authors independently extracted data from the same studies simultaneously, double checking after extraction. A second round of examination was conducted on all the extracted contents by another author. We employed a measurement tool to assess systematic reviews (AMSTAR-2) to evaluate the methodological rigor of the included systematic reviews (SRs), synthesized the GRADE results as reported, and conducted a narrative synthesis. The research protocol was registered on PROSPERO (CRD42023388884).ResultsSeventy-one Cochrane reviews involving 3022 trials were included in this comprehensive analysis. The two predominant smoking cessation interventions were pharmacotherapy (24 SRs) and non-pharmacological therapy (31SRs). Overall, the methodological quality of all the reviews was good. Compared with placebo, the point effect size for each Cochrane review on relative risk (RR) regarding pharmacotherapies for prolonged abstinence rate ranged from 1.11 to 3.34, demonstrating high- or moderate-certainty evidence; whereas for non-pharmacological therapies, it varied from 0.79 to 25.38, but substantial heterogeneity was observed in most meta-analysis (I2>50%). Four studies investigating pharmacotherapies as interventions, adverse events were reported but no significant differences in outcomes were observed.ConclusionsPharmacotherapy demonstrated some efficacy in promoting prolonged abstinence rate, while the effectiveness of different non-pharmacological interventions for smoking cessation varied widely, highlighting the need for further research on the integration of pharmacotherapy and non-pharmacological therapies.
| S-EPMC11603414 | biostudies-literature