2.6 Quality assessment
Risk of bias was used the Cochrane Collaboration’s risk of bias
assessment tool [13]. Two authors (J Jiang and YP Huang)
independently rated each study as “high”, “low”, “unclear” for
risk of bias assessment, W Zhang helped resolve when disagreements were
reached. The evaluation tools mainly include the method of random
allocation sequence, blinding of subjects or trial personnel, blinding
of outcome assessors, completeness of outcome data, selective reporting,
allocation concealment, and other sources of bias.