Table 2. Quality Assessment of Reviewed Case-Control Studies.
| Study | Case defined with independent validation | Representativeness of the cases | Selection of controls from community | Statement that controls have no history of outcome | Cases and controls matched and/or adjusted by factors | Ascertain exposure by blinded structured interview | Same method of ascertainment for cases and controls | Same response rate for both groups | Overall Score |
|---|---|---|---|---|---|---|---|---|---|
| Parslov, 2000 | 1 | 1 | 1 | 1 | 2 | 0 | 1 | 1 | 8 |
| Salazar-Martinez, 1999 | 1 | 1 | 0 | 0 | 2 | 1 | 1 | 1 | 7 |
| Parazzini, 1998 | 1 | 1 | 0 | 0 | 2 | 1 | 1 | 1 | 7 |
| Kalandidi, 1996 | 1 | 1 | 0 | 0 | 2 | 1 | 1 | 1 | 7 |
| Shu, 1993 | 1 | 1 | 1 | 0 | 1 | 1 | 1 | 1 | 7 |
| Koumantaki, 1989 | 1 | 1 | 0 | 0 | 0 | 1 | 1 | 1 | 5 |
| Kelsey, 1982 | 1 | 1 | 0 | 1 | 2 | 1 | 1 | 1 | 8 |
| Baron, 1986 | 1 | 1 | 0 | 1 | 0 | 1 | 1 | 1 | 6 |
| Castellsague, 1993 | 1 | 1 | 1 | 0 | 2 | 1 | 1 | 1 | 8 |
| Dahlgren, 1991 | 1 | 1 | 1 | 0 | 0 | 1 | 1 | 1 | 6 |
| Damon, 1960 | 1 | 1 | 0 | 1 | 0 | 1 | 1 | 1 | 6 |
| Elwood, 1977 | 1 | 1 | 1 | 0 | 1 | 0 | 1 | 1 | 6 |
| Fox, 1970 | 1 | 1 | 1 | 0 | 1 | 1 | 1 | 1 | 7 |
| Garnet, 1958 | 1 | 1 | 0 | 1 | 0 | 0 | 1 | 1 | 5 |
| Henderson, 1983 | 1 | 1 | 1 | 0 | 1 | 1 | 1 | 1 | 7 |
| Hirose, 1996 | 1 | 1 | 0 | 1 | 2 | 0 | 1 | 1 | 7 |
| Hosono, 2011 | 1 | 1 | 0 | 1 | 2 | 0 | 1 | 1 | 7 |
| Jaakkola, 2011 | 0 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 7 |
| Kakuta, 2009 | 1 | 1 | 0 | 1 | 2 | 0 | 1 | 1 | 7 |
| Lawrence, 1989 | 1 | 1 | 1 | 0 | 2 | 1 | 1 | 1 | 8 |
| Lesko, 1991 | 1 | 1 | 0 | 1 | 2 | 1 | 1 | 1 | 8 |
| Levi, 1991 | 1 | 1 | 0 | 1 | 0 | 1 | 1 | 1 | 6 |
| Littman, 2001 | 1 | 1 | 1 | 1 | 2 | 1 | 1 | 1 | 9 |
| Macdonald, 1977 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 8 |
| Newcomer, 2001 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 8 |
| Pettersson, 1986 | 1 | 1 | 1 | 1 | 2 | 1 | 1 | 1 | 9 |
| Spengler, 1981 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 8 |
| Wynder, 1966 | 1 | 1 | 0 | 1 | 0 | 1 | 1 | 1 | 6 |
| Wang, 1990 | 1 | 1 | 0 | 1 | 2 | 1 | 1 | 1 | 8 |
| Hachisuga, 1998 | 1 | 1 | 0 | 1 | 2 | 1 | 1 | 1 | 8 |
| Brons, 2015 | 0 | 1 | 1 | 0 | 1 | 1 | 1 | 1 | 6 |
| La Vecchia, 1984 | 1 | 1 | 0 | 1 | 1 | 1 | 1 | 1 | 7 |
| Salmi, 1979 | 1 | 1 | 1 | 0 | 2 | 1 | 1 | 1 | 8 |
| Asakura, 2009 | 1 | 1 | 1 | 1 | 2 | 0 | 1 | 0 | 7 |
| Hao, 2009 | 0 | 1 | 1 | 1 | 2 | 0 | 1 | 1 | 7 |
1 means 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 equal relevant importance.