https://www.selleckchem.com/products/iso-1.html Authors, editors and peer-reviewers should make an effort to improve completeness and adequacy of Cochrane RoB assessment in non-Cochrane reviews. OBJECTIVES Classical meta-analyses routinely treated studies with no events in both arms non-informative and excluded them from analyses. This study assessed whether such studies contain information and have influence on the conclusions of meta-analyses. DESIGN and setting We collected meta-analyses of binary outcomes with at least one study having no events in both arms from Cochrane systematic reviews (2003-2018). We used the generalized linear mixed model to reanalyze these meta-analyses by two approaches one including studies with no events in both arms and one excluding such studies. The magnitude and direction of odds ratio (OR), p-value, and width of 95% confidence interval (CI) were compared. A simulation study was conducted to examine the robustness of results. RESULTS We identified 442 meta-analyses. In comparing paired meta-analyses that included studies with no events in both arms versus those not, 8 (1.80%) resulted in different directions on OR; 41 (9.28%) altered conclusions on statistical significance. Substantial changes occurred on p-value (55.66% increased, 44.12% decreased) and the width of 95% CI (50.68% inflated, 49.32% declined) when excluding studies with no events. Simulation study confirmed these findings CONCLUSIONS Studies with no events in both arms are not necessarily non-informative. Excluding such studies may alter conclusions. OBJECTIVES To examine the design, conduct, and analysis of systematic reviews assessing drug safety through a cross-sectional survey. STUDY DESIGN AND SETTING We searched PubMed to identity systematic reviews published in the Cochrane Database of Systematic Reviews and Core Clinical Journals indexed in 2015, and randomly sampled systematic reviews assessing drug effects at a 11 ratio of Cochrane and non-Cochrane reviews