Table 3. Assessment of the risk of bias.
| Study participation | Prognostic factor measurement | Outcome measurement | Study confounding | Statistical analysis and reporting | Overall risk of bias | |
|---|---|---|---|---|---|---|
| Tang and Hsieh 19 (2017) | Low | High | Low | High | High | High |
| Cantinotti et al 21 (2018) | Low | Low | Low | High | Low | Moderate |
| Gupta et al 20 (2018) | Moderate | Moderate | Moderate | High | Low | Moderate |
| Girona-Alarcon et al 22 (2020) | Low | Low | Low | Moderate | High | Moderate |
Note: Low, moderate, and high refer to the risk of bias for each criterion.