Table 1.

Characteristics of the included studies.

Author	Year	Country	Ethnicity	Control source	Genotyping method	Number		Quality score	Hardy–Weinberg equilibrium
						Case	Control
Sarbia	2003	Germany	White	PB	PCR-RFLP	62	253	7	0.602
Zhang	2003	China	Asian	HB	PCR-RFLP	193	141	8	0.765
Zhang	2003	Germany	White	HB	PCR-RFLP	257	252	9	0.603
Marjani	2010	Iran	White	HB	PCR-RFLP	93	50	7	0.467
Hamajima	2002	Japan	Asian	HB	PCR-CTPP	102	399	8	0.256
von Rahden	2005	Germany	White	HB	PCR-RFLP	140	260	8	0.166
Feng	2008	China	Asian	HB	PCR-RFLP	201	201	6	0.144
Umar M	2012	India	White	PB	PCR-RFLP	200	200	6	0.865
Zhang WC	2006	China	Asian	PB	PCR-RFLP	106	106	7	0.001*
Zhou Y	2006	China	Asian	PB	PCR-RFLP	96	192	7	0.729
Di Martino	2007	UK	White	HB	PCR-RFLP	144	94	8	0.986
Malik MA	2012	India	White	PB	PCR-RFLP	135	195	8	0.307
Yin J	2014	China	Asian	HB	NA	629	686	9	0.142

HB, hospital-based design; NA, not available; PB, population-based design; PCR-CTPP, polymerase chain reaction-confronting two-pair primers; PCR-RFLP, polymerase chain reaction-restriction fragment length polymorphism.

^*p < 0.05.