Table 2.

Newcastle-Ottawa for case-control studies.

Case control	Durmus et al. (30)	Lygidakis et al. (23)	Beentjes et al. (34)	Ahmadi et al. (24)	Ghanim et al. (36)	Muratbegovic et al. (38)	Whatling and Fearne (39)
Selection
1) Is the case definition adequate?	*	*	–	*	*	*	*
2) Representativeness of the cases	*	*	–	*	*	*	*
3) Selection of controls	*	*	–	–	*	*	*
4) Definition of controls	*	*	–	*	*	*	*
Comparability
1) Comparability of cases and controls on the casis of the design or analysis	**	**	*	*	*	**	**
Exposure
1) Ascertainment of exposure	*	*	–	*	*	*	-
2) Same method of ascertainment for cases and controls	*	*	–	*	*	*	*
3) Non-response rate	–	*	–	–	*	*	*

The * and ** symbols indicate score that each article received in the quality assessment.