Table 1 Score distribution of quality assessment based on Newcastle-Ottawa scale
Items | Yin et al. [10] | Wu et al. [23] | Zhong et al. [24] | Suya et al. [25] | Gao et al. [26] | Koptan et al. [27] | Du et al. [28] | Zhang et al. [29] |
|---|---|---|---|---|---|---|---|---|
Selection | ||||||||
Is the case definition adequate | ☆ | ☆ | ☆ | ☆ | ☆ | ☆ | ☆ | ☆ |
Representativeness of the cases | ☆ | ☆ | ☆ | ☆ | ☆ | ☆ | ☆ | ☆ |
Selection of controls | ☆ | ☆ | ☆ | ☆ | - | ☆ | - | ☆ |
Defnition of controls | ☆ | ☆ | ☆ | ☆ | ☆ | ☆ | ☆ | ☆ |
Comparability | ||||||||
Study controls for the most important factor | ☆ | ☆ | ☆ | ☆ | ☆ | ☆ | ☆ | ☆ |
Study controls for any additional factor | ☆ | ☆ | - | - | ☆ | - | - | - |
Exposure | ||||||||
Ascertainment of exposure | ☆ | ☆ | ☆ | ☆ | ☆ | ☆ | ☆ | ☆ |
Same method of ascertainment for cases and controls | ☆ | ☆ | ☆ | ☆ | ☆ | ☆ | ☆ | ☆ |
Non-response rate | - | - | - | - | - | - | - | - |
Total scores | 8 | 8 | 7 | 7 | 6 | 7 | 6 | 7 |