Table 2.

Quality assessment of studies included in the meta-analysis.

Criteria	Score	Marziniak et al. (18)	Lemos et al. (19)	Sutherland et al. (20)	Coskun et al. (21)	Azimova et al. (25)
Representativeness of cases
Consecutive/randomly selected from case population with clearly defined sampling frame	2	X	X	X	X	X
Consecutive/randomly selected from case population without clearly defined sampling frame or with extensive inclusion/exclusion criteria	1
No method of selection described	0
Representativeness of controls
Controls were consecutive/randomly drawn from the same sampling frame as cases	2	X	X	X	X	X
Controls were consecutive/randomly drawn from a different sampling frame as cases	1
Not described	0
Ascertainment of migraine
Clearly described objective criteria for diagnosis of migraine	2	X	X	X	X	X
Diagnosis of migraine by patient self-report or by patient history	1
Not described	0
Quality control of genotyping methods
Clearly described a different genotyping assay to confirm the data	1		X
Not described	0	X		X	X	X
Hardy–Weinberg equilibrium
Hardy–Weinberg equilibrium in controls	2	X	X	X	X
Hardy–Weinberg disequilibrium in controls	1					X
No checking for Hardy–Weinberg disequilibrium	0
Association assessment
Assess association between genotypes and migraine with appropriate statistics and adjustment for confounders	2		X	X	X
Assess association between genotypes and migraine with appropriate statistics without adjustment for confounders	1	X				X
Inappropriate statistics used	0
Total score	11	9	11	10	10	8