Table 2.
Bias risk assessment results of included studies.
| ① | ② | ③ | ④ | ⑤ | ⑥ | ⑦ | ⑧ | ⑨ | ⑩ | ⑪ | Score | level | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Cai H (2019) | Y | Y | Y | Y | Y | N | N | Y | N | Y | N | 7 | Medium |
| Tan CQ (2015) | Y | N | Y | Y | Y | N | N | Y | N | Y | UN | 6 | Medium |
| Liang TY (2015) | Y | Y | N | N | Y | N | Y | Y | Y | Y | N | 7 | Medium |
| Su TT (2016) | Y | Y | N | Y | Y | N | Y | Y | N | Y | UN | 7 | Medium |
| Jin J (2019) | Y | N | N | Y | Y | N | N | Y | N | Y | N | 5 | Medium |
| Yan HM (2015) | Y | N | N | Y | Y | N | N | Y | N | Y | N | 5 | Medium |
| Liu Y (2016) | Y | N | Y | Y | Y | N | N | Y | N | Y | N | 6 | Medium |
| Ma LJ (2012) | Y | N | N | Y | Y | N | N | Y | UN | Y | UN | 5 | Medium |
| Yang Q (2008) | Y | N | N | N | Y | N | N | Y | Y | Y | N | 5 | Medium |
| Wang JL (2008) | Y | N | Y | Y | Y | N | N | Y | N | Y | UN | 6 | Medium |
| He LY (2004) | Y | N | N | N | Y | N | N | Y | Y | Y | N | 5 | Medium |
| Zhang XY (2006) | Y | N | Y | Y | Y | N | N | Y | Y | Y | N | 7 | Medium |
| Cao XX (2007) | Y | N | Y | N | Y | N | N | Y | Y | Y | N | 6 | Medium |
| Yang J (2015) | Y | Y | Y | Y | Y | N | Y | Y | N | Y | UN | 8 | High |
| Zhang YR (2021) | Y | Y | Y | N | Y | N | Y | Y | Y | Y | N | 8 | High |
| Xu YJ (2020) | Y | Y | Y | N | Y | N | Y | Y | Y | Y | N | 8 | High |
| Johansen ML (2016) | Y | Y | Y | N | Y | N | Y | Y | Y | Y | N | 8 | High |
| Tavakoli N (2018) | Y | N | Y | N | Y | N | N | Y | Y | Y | UN | 6 | Medium |
| Singh GP (2013) | Y | N | N | Y | Y | N | N | Y | N | Y | N | 5 | Medium |
| Hendy A (2020) | Y | Y | N | Y | Y | N | N | Y | N | Y | N | 6 | Medium |
| Chao W (2020) | Y | N | Y | N | Y | N | N | Y | Y | Y | N | 6 | Medium |
① Whether the source of the data is clear (investigation, literature review); ② Are the inclusion and exclusion criteria for exposure and no exposure groups (cases and controls) listed or referred to previous publications? ③ Is a time period given for identifying patients? ④If not from the population, are the subjects continuous? ⑤Does the subjective factor of the evaluator cover up other aspects of the research object? ⑥ Describe any assessment for quality assurance (e.g. testing/ retesting of primary outcome indicators); ⑦The reasons for excluding any patients from the analysis were explained; ⑧It describes how to evaluate and/ or control the confounding factors; ⑨ If possible, the explanation is that how to deal with the loss of data; ⑩ The response rate and data collection were summarized the integrity of the system; ⑪ If there is a follow-up, identify the percentage of expected incomplete data or follow-up results.