TABLE 2.
The results of risk of bias of included RCTs.
| 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 source of bias |
| Ma (15) | Unclear | Unclear | Unclear | Unclear | Low | Low | Low |
| Zheng et al. (16) | Low | Unclear | Unclear | Unclear | Low | Low | Low |
| Zhang (20) | Unclear | Unclear | Unclear | Unclear | Low | Low | Low |
| Xu (14) | Unclear | Unclear | Unclear | Unclear | Low | Low | Low |
| Li (17) | Unclear | Unclear | Unclear | Unclear | Low | Low | Low |
| Wu (19) | Unclear | Unclear | Unclear | Unclear | Low | Low | Low |
| Wang (18) | Unclear | Unclear | Unclear | Unclear | Low | Low | Low |
| Xiong (21) | Unclear | Unclear | Unclear | Unclear | Low | Low | Low |