Table 3.
Quality assessment of reviewed case–control studies
| Reference | Cases defined with independent validation | Representativeness of the cases | Controls selected from community | Inclusion of statement that controls had no history of outcome | Cases and controls matched and/or adjusted by factors | Exposure ascertained by blinded structured interview | Same method of ascertainment used for cases and controls | Same response rate for both groups |
|---|---|---|---|---|---|---|---|---|
| Kune et al. (1987)64 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 0 |
| Takayama et al. (2013)48 | 1 | 1 | 0 | 1 | 2 | 0 | 1 | 0 |
| Wang et al. (2012)49 | 1 | 1 | 1 | 1 | 2 | 1 | 1 | 0 |
| Giles et al. (1994)47 | 1 | 1 | 1 | 1 | 2 | 0 | 1 | 0 |
| Chen et al. (1991)50 | 1 | 1 | 1 | 1 | 2 | 1 | 1 | 0 |
| Zhang et al. (1998)57 | 1 | 1 | 0 | 1 | 2 | 1 | 1 | 0 |
| Yu et al. (2002)56 | 1 | 1 | 1 | 1 | 2 | 1 | 1 | 0 |
| Soliman et al. (2010)54 | 1 | 1 | 0 | 1 | 2 | 1 | 1 | 0 |
| Pan et al.52 (2004) | 1 | 1 | 1 | 1 | 2 | 0 | 1 | 1 |
| Raimondi et al.53 (2010) | 1 | 1 | 1 | 0 | 2 | 1 | 1 | 0 |
| Trichopoulos et al. (1985)55 | 1 | 1 | 0 | 0 | 0 | 1 | 1 | 0 |
| Hoshiyama & Sasaba (1992)51 | 1 | 1 | 1 | 0 | 2 | 1 | 1 | 0 |
| Jackson et al. (2013)58 | 1 | 1 | 0 | 1 | 2 | 1 | 1 | 0 |
| Moller et al. (2013)59 | 1 | 1 | 1 | 0 | 2 | 0 | 1 | 1 |
| Petridou et al. (2002)60 | 1 | 1 | 0 | 1 | 2 | 0 | 1 | 0 |
| Yamamura et al. (2013)61 | 1 | 1 | 1 | 0 | 2 | 0 | 1 | 0 |
| Ibiebele et al. (2012)62 | 1 | 1 | 1 | 1 | 2 | 0 | 1 | 1 |
| Jain et al. (1999)63 | 1 | 1 | 1 | 0 | 2 | 1 | 1 | 0 |
| Samoli et al. (2010)67 | 1 | 1 | 0 | 1 | 2 | 1 | 1 | 1 |
| Liu et al. (2014)65 | 1 | 1 | 1 | 0 | 2 | 0 | 1 | 1 |
aScoring: 1 means the study adequately fulfilled a quality criterion (2 for case–control, fully matched and adjusted), 0 means it did not. Quality scale does not imply that items are of equally relevant importance.