2.6 Statistical analysis
A meta-analysis of the summary statistics from individual trials was performed. The statistical analysis was completed by an independent statistician (C-CF). The differences in dichotomous variables and outcome endpoints were reported as an odds ratio (OR) or risk ratio (RR) with 95% confidence intervals (CIs). The continuous variables were analyzed using weighted mean differences (WMD) or standard mean differences (SMD). Fixed- and random-effects models used weighting based on an inverse variance, which was calculated according to DerSimonian and Laird11. The between-study heterogeneity was reflected by I 2>50%, with a P <0.05 deemed statistically significant. In cases of statistical heterogeneity, sensitivity analyses were performed to assess the contribution of each study to the pooled estimate by sequentially excluding individual trials and recalculating the pooled RR estimate for the remaining studies12. When the pooled analysis still yielded significant heterogeneity, the random-effects model was used. The statistical analysis was performed using the Review Manager (version 5.3; Copenhagen : The Nordic Cochrane Center, The Cochrane Collaboration, 2014).