Table 2.
Quality assessment of studies.
| References | Adequate sequence generation | Allocation concealment | Blinding of participation and personnel | Blinding of outcome assessment | Incomplete outcome data addressed | Selective outcome reporting avoided | Other sources of bias |
|---|---|---|---|---|---|---|---|
| Sun (2017) | Yes | Yes | Yes | Yes | Yes | Yes | Unclear |
| Shao (2016) | Yes | No | No | Unclear | Yes | Yes | Unclear |
| Liu et al. (2015a) | Yes | No | No | Unclear | Yes | Yes | Unclear |
| Cai et al. (2016) | Yes | Unclear | No | Unclear | Yes | Yes | Unclear |
| Zeng et al. (2015) | Yes | Unclear | No | Unclear | Yes | Yes | Unclear |
| Wang (2014) | Yes | Unclear | No | Unclear | Yes | Yes | Unclear |
| Lu (2014) | Yes | Yes | No | Unclear | Yes | Yes | Unclear |
| Zhai (2012) | Yes | No | No | Unclear | Yes | Yes | Unclear |
| Bai et al. (2012) | Yes | Unclear | No | Unclear | Yes | Yes | Unclear |
| Li et al. (2012) | Yes | Yes | No | Unclear | Yes | Yes | Unclear |
| Yang (2011) | Yes | Yes | No | Unclear | Yes | Yes | Unclear |
| Sun and Wu (2011) | Yes | No | No | Unclear | Yes | Yes | Unclear |
| Kang (2011) | Yes | Yes | No | Unclear | Yes | Yes | Unclear |
| Jiang (2011) | Yes | Yes | No | Unclear | Yes | Yes | Unclear |
| Jia and Meng (2011) | Yes | No | No | Unclear | Yes | Yes | Unclear |
| Lin et al. (2010) | Yes | No | No | Unclear | Yes | Yes | Unclear |
| Huang et al. (2008) | Yes | No | No | Unclear | Yes | Yes | Unclear |
| Shi and Wei (2019) | Yes | Unclear | No | Unclear | Yes | Yes | Unclear |
| Zhou J. et al. (2019) | Yes | Unclear | No | Unclear | Yes | Yes | Unclear |
| Feng (2013) | Yes | Yes | No | Yes | Yes | Yes | No |
| Wang et al. (2019) | Yes | Unclear | No | Unclear | Yes | Yes | Unclear |
| Li et al. (2019) | Yes | Unclear | No | Yes | Yes | Yes | No |
| Zhang et al. (2017) | Yes | Yes | No | Unclear | Yes | Yes | No |
| Wang H. et al. (2017) | Yes | No | No | No | Yes | Yes | Unclear |
| Zhou H. et al. (2019) | Yes | Unclear | No | Unclear | Yes | Yes | Unclear |
| Wang Z. et al. (2017) | Yes | Unclear | No | Unclear | Yes | Yes | Unclear |
| Wang et al. (2019) | Yes | Unclear | No | Unclear | Yes | Yes | Unclear |
| Wang and Li (2018) | Yes | Unclear | No | Unclear | Yes | Yes | Unclear |
| Yang (2014) | Yes | Unclear | No | Unclear | Yes | Yes | Unclear |
| Ma et al. (2018) | Yes | Unclear | No | Unclear | Yes | Yes | Unclear |
| Jia and Lv (2018) | Yes | Unclear | No | Unclear | Yes | Yes | Unclear |
| Liu (2017) | Yes | Unclear | No | Unclear | Yes | Yes | Unclear |
| Liu et al. (2015b) | Yes | Unclear | No | Unclear | Yes | Yes | Unclear |
| Sun et al. (2013) | Yes | Unclear | No | Unclear | Yes | Yes | Unclear |
| Liu and Feng (2013) | Yes | Unclear | No | Unclear | Yes | Yes | Unclear |
| Wang et al. (2014) | Yes | Unclear | No | Unclear | Yes | Yes | Unclear |
| Li and Zhang (2008) | Yes | No | No | No | Yes | Yes | Unclear |