Quality assessment
The overall risk of bias among the four nonrandomized studies according to the Newcastle-Ottawa Quality Assessment Scale (NOS) was 7.5. The overall risk of bias of the six randomized controlled studies evaluated by the Cochrane Collaboration’s Risk of Bias Tool was low. The risk of bias assessment is summarized in Figures S1 and S2.
As ten studies were included in the meta-analysis, we were able to test for funnel plot asymmetry to assess possible publication bias. Visual inspection of the funnel plots revealed no indication of publication bias, Egger test also indicates no statistical significance in asymmetry (p=0.5). (Figure S3).