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).