Table 2 Quality of included studies
Item/Study | Nagaya et al. 2018 [13] | Hashemi et al. 2018 [14] | Clarke et al. 2012 [15] | Wei et al. 2011 [16] | Jia et al. 2010 [17] | Clarke et al. 2009 [18] | Yuanyuan et al. 2018 [12] |
|---|---|---|---|---|---|---|---|
Adequate definition of cases | ★ | ★ | ★ | ★ | ★ | ★ | ★ |
Representativeness of cases | ☆ | ☆ | ☆ | ☆ | ☆ | ☆ | ☆ |
Selection of control subjects | ☆ | ☆ | ☆ | ☆ | ☆ | ☆ | ☆ |
Definition of control subjects | ★ | ★ | ★ | ★ | ★ | ★ | ★ |
Control for important factor or additional factor | ★☆ | ★☆ | ★☆ | ★☆ | ☆☆ | ☆☆ | ★☆ |
Exposure assessment | ★ | ★ | ★ | ★ | ★ | ★ | ★ |
Same method of ascertainment for all subjects | ★ | ★ | ★ | ★ | ★ | ★ | ★ |
Non-response rate | ★ | ★ | ★ | ★ | ★ | ★ | ★ |