Risk of bias assessment in included studies based on the Cochrane handbook
| Included studies | Random sequence generation | Concealment of allocation | Blinding of participants and personnel | Blinding of outcome assessment | Incomplete outcome data | Selective reporting | Other bias | Risk of bias |
|---|---|---|---|---|---|---|---|---|
| Teekachunhatean et al30 | ? | + | + | + | + | ? | + | Unclear |
| Yu and Zhang39 | ? | ? | − | ? | + | ? | + | High |
| Cao et al48 | Random number table | ? | − | ? | ? | ? | + | High |
| Gu49 | ? | ? | − | ? | + | ? | + | High |
| Yu50 | ? | ? | − | ? | + | ? | + | High |
| Zhang and Sun51 | ? | ? | − | ? | ? | ? | + | High |
| Zhong and Zhong52 | ? | ? | − | ? | ? | ? | + | High |
| Dong53 | ? | ? | − | ? | + | ? | + | High |
| Huang and et al54 | ? | ? | − | ? | + | ? | + | High |
| Jiang55 | ? | ? | − | ? | ? | ? | + | High |
| Wang56 | ? | ? | − | ? | ? | ? | + | High |
| Zhou and Wang57 | ? | ? | − | ? | ? | ? | + | High |
+, Low risk of bias; −, high risk of bias; ?, unclear risk of bias.