Data extraction and quality assessment
Two investigators (CL, HQH) reviewed the full text of the eligible RCTs and extracted information. The information included setting (in/out patients), diagnostic criteria, sample size, average age, intervention, comparison, outcomes, withdrawal/dropout, and adverse events. All information was double-checked by referring to the original articles when an inconsistency existed.
The quality of the included RCTs was assessed by two investigators (CL, HQH) independently using Cochrane Collaboration’s tool for assessing the risk of bias.72 Based on the authors’ description in the original references, the quality of each of the included studies was classified as having a low, unclear, or high risk of bias, according to the items for judging risk of bias in the ‘Risk of bias’ assessment tool in the Cochrane handbook.73 Disagreements were resolved by discussing with the third author (GC) and reaching a consensus among authors.