Table 3 Risk-of-bias assessment of the included studies, according to the modified Newcastle-Ottawa Scale (NOS)
NOS items / Study ID | Wu 2017 | Kevin 2017 | Levent 2016 | Yin 2014 | Mahaluxmivala 2005 |
|---|---|---|---|---|---|
Is the case definition adequate? | ★ | ★ | ★ | ★ | ★ |
Representativeness of the cases | ★ | ● | ★ | ● | ★ |
Selection of controls | ● | ★ | ● | ● | ● |
Definition of controls | ★ | ★ | ★ | ★ | ★ |
Study controls for the most important factor (i.e., age) | ★ | ★ | ● | ★ | ● |
Study controls for the second important factor (i.e., sex) | ★ | ★ | ★ | ★ | ● |
Was the measurement method described? | ★ | ★ | ★ | ★ | ★ |
Were the methods of measurements similar for cases and controls? | ★ | ★ | ★ | ★ | ★ |
Non-response rate | ★ | ★ | ★ | ● | ★ |
Total Score | 8 | 8 | 7 | 6 | 6 |