![]() ![]() Meta-analyses may therefore include data from one or more small studies which, individually, do not have power to detect a modest intervention effect. Such criteria seldom address sample size. Systematic reviews of intervention studies aim to synthesise all available evidence meeting pre-specified eligibility criteria. This does not alter the authors' adherence to all the PLOS ONE policies on sharing data and materials, as detailed online in the guide for authors. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.Ĭompeting interests: RMT and JPTH declare that no competing interests exist. 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.įunding: This work was funded by Medical Research Council grants U105285807 and U105260794. Received: NovemAccepted: FebruPublished: March 27, 2013Ĭopyright: © 2013 Turner et al. PLoS ONE 8(3):Ĭopenhagen University Hospital Gentofte, Denmark 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.Ĭitation: Turner RM, Bird SM, Higgins JPT (2013) The Impact of Study Size on Meta-analyses: Examination of Underpowered Studies in Cochrane Reviews. 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 median of summary relative risks was 0.75 across all meta-analyses (inter-quartile range 0.55 to 0.89). 34% of the meta-analyses themselves were adequately powered. 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. 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. We defined adequate power as ≥50% power to detect a 30% relative risk reduction. For 14,886 meta-analyses of binary outcomes from 1,991 Cochrane reviews, we calculated power per study within each meta-analysis. ![]()
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |