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| Study | Selection | Comparability | Outcome | Total score |
|||||
|---|---|---|---|---|---|---|---|---|---|
| Representativeness | Selection of the non-exposed cohort |
Ascertainment of exposure | Demonstration | Assessment of outcome | Follow up | Adequacy of follow up | |||
| Bischof (15) | ★ | ★ | ★ | – | ★ | ★ | ★ | – | 6 |
| Yu (16) | ★ | ★ | ★ | – | ★ | ★ | ★ | – | 6 |
| Liu (17) | ★ | ★ | ★ | – | ★ | ★ | ★ | – | 6 |
| Zhang (18) | ★ | ★ | ★ | – | ★ | ★ | ★ | – | 6 |
| Wong (19) | ★ | ★ | ★ | – | ★★ | ★ | ★ | – | 7 |
⌈, Each star (⌈) denotes one point.
