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| Author | Sequence generation | Allocation concealment | Blinding | Incomplete outcome | Selective outcome report | Other source of bias |
|---|---|---|---|---|---|---|
| Lee 2008 (12) | Low | Unclear | Low | Low | Unclear | Low |
| Qin 2018 (23) | Low | Low | Low | Low | Low | Unclear |
| Sahin 2015 (24) | Low | Unclear | Low | Low | Unclear | Low |
| Zhou 2017 (25) | Low | Low | Low | Low | Unclear | Unclear |
