9/2/2023 0 Comments Cochrane meta analysisHowever, underpowered studies made up the entirety of the evidence in most Cochrane reviews. When 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. 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. Bias due to selective inclusion and reporting of outcomes and analyses in systematic reviews of randomised trials of healthcare interventions. The results were presented and analyzed by weighted mean difference (WMD), Standard Mean Difference (SMD) and risk ratio (RR) at their 95 confidence interval (CI). 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. This Meta-analysis was registered on PROSPERO (CRD42022351038) and data were processed using Review Manager 5.4 and Stata 16.0SE. 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. Cochrane Handbook for Systematic Reviews of Interventions version 6.3 (updated February 2022). 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. 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.įor 14,886 meta-analyses of binary outcomes from 1,991 Cochrane reviews, we calculated power per study within each meta-analysis. The relative influence of adequately powered and underpowered studies in published meta-analyses has not previously been explored. Most meta-analyses include data from one or more small studies that, individually, do not have power to detect an intervention effect.
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