Risk of bias for each included randomized trial (14)
| Study | Random sequence generation (selection bias) | Allocation concealment (selection bias) | Blinding of participants and personnel (performance bias) | Blinding of outcome assessment (detection bias) | Incomplete outcome data (attrition bias) | Selective reporting (reporting bias) | Other bias |
|---|---|---|---|---|---|---|---|
| Kim et al. (17) | + | + | ? | + | + | + | ? |
| Kim et al. (18) | + | + | ? | + | + | + | ? |
| Kim et al. (19) | + | + | ? | + | + | + | ? |
+ = low risk of bias; ? = unclear risk of bias.