Table 2.
Quality assessment of included studies.
| Study | Adequate definition of cases | Representativeness of cases | Selection of control subjects | Definition of control subjects | Control for important factor | Exposure assessment | Same method of ascertainment for all subjects | Nonresponse rate | Total |
|---|---|---|---|---|---|---|---|---|---|
| Altintoprak AE, 2012 | 1 | 0 | 0 | 1 | 2 | 1 | 1 | 1 | 7 |
| Celorrio D, 2016 | 1 | 1 | 1 | 1 | 2 | 1 | 1 | 1 | 9 |
| Enoch MA, 2006 | 1 | 1 | 1 | 1 | 2 | 1 | 1 | 1 | 9 |
| Gao LB, 2011 | 1 | 0 | 0 | 1 | 1 | 1 | 1 | 1 | 6 |
| Hallikainen T, 2000 | 1 | 0 | 0 | 1 | 1 | 1 | 1 | 1 | 6 |
| Ishiguro H, 1999 | 1 | 0 | 0 | 1 | 2 | 1 | 1 | 1 | 7 |
| Kweon YS, 2005 | 1 | 0 | 1 | 1 | 1 | 1 | 1 | 1 | 7 |
| Liu Y, 2005 | 0 | 1 | 1 | 1 | 2 | 1 | 1 | 1 | 8 |
| Malhotra S, 2016 | 1 | 0 | 0 | 1 | 1 | 1 | 1 | 1 | 6 |
| Nakamura A, 2001 | 1 | 0 | 1 | 1 | 1 | 1 | 1 | 1 | 7 |
| Nikolac M, 2013 | 1 | 0 | 0 | 1 | 1 | 1 | 1 | 1 | 6 |
| Pombo S, 2017 | 1 | 0 | 0 | 1 | 0 | 1 | 1 | 1 | 5 |
| Samochowiec J, 2008 | 1 | 0 | 1 | 1 | 2 | 1 | 1 | 1 | 8 |
| Schellekens A F, 2012 | 1 | 1 | 1 | 1 | 2 | 1 | 1 | 1 | 9 |
| Sery O, 2006 | 1 | 0 | 0 | 1 | 2 | 1 | 1 | 1 | 7 |
| Soyka M, 2015 | 1 | 0 | 1 | 1 | 2 | 1 | 1 | 1 | 8 |
| Voisey J, 2011 | 1 | 0 | 1 | 1 | 1 | 1 | 1 | 1 | 7 |
| Wang X, 2011 | 1 | 0 | 0 | 1 | 2 | 1 | 1 | 1 | 7 |
| Choi TY, 2006 | 1 | 0 | 0 | 1 | 2 | 1 | 1 | 1 | 7 |
| Zhang X, 2013 | 1 | 1 | 1 | 1 | 0 | 1 | 1 | 1 | 7 |