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The quality of included Case-Control Studies.
| Study | Is the Case Definition Adequate? | Representativeness of the Cases | Selection of Controls | Definition of Controls | Comparability of Cases and Controls | Ascertainment of Exposure | Use the same method to determine case and control exposure factors | Non-Response Rate | Total |
|---|---|---|---|---|---|---|---|---|---|
| Qu XK [26] | ★ | ★ | ★★ | ★ | ★ | 6 | |||
| Xia WG [11] | ★ | ★ | ★★ | ★ | ★ | 6 | |||
| Yao KT [27] | ★ | ★ | ★★ | 4 | |||||
| Xiao Q [28] | ★ | ★ | ★★ | ★ | ★ | 6 | |||
| Cheng DZ [29] | ★ | ★ | ★★ | ★ | ★ | 6 | |||
| Shi J [13] | ★ | ★★ | 3 | ||||||
| Yang MB [30] | ★ | ★ | ★★ | ★ | ★ | ★ | 7 |
