Table 2. Risk of bias assessment of the included studies according to the modified Newcastle-Ottawa Scale (NOS).
| NOS items / Study ID | Zivkovic 2011 |
EL-Nakeeb 2006 |
Musabak 2005 |
Rajaee 2004 |
El-Ageb 2002 |
Espinosa 2002 |
Hughes 1998 |
Kang 1998 |
Ji 1992 |
Bergman 1990 |
|---|---|---|---|---|---|---|---|---|---|---|
| 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 of aPLs described? | ★ | ★ | ★ | ★ | ★ | ★ | ★ | ★ | ★ | ★ |
| Were the methods of measurements similar for cases and controls (i.e., ELISA)? | ★ | ★ | ★ | ★ | ★ | ★ | ★ | ★ | ★ | ★ |
| Non-response rate | ★ | ★ | ★ | ★ | ★ | ★ | ★ | ★ | ★ | ★ |
| Total Score | 6 | 8 | 9 | 6 | 8 | 8 | 6 | 6 | 7 | 6 |
★ was awarded when the respective information was available.
● was awarded if the respective information was unavailable.