Table 1. Characteristics of studies included in this meta-analysis.

Gene	Author	Year	Ethnicity	Country	Sample Size		Genotyping	Matching Criteria	MAF in		HWE
Polymorphism	Reference				Case	Control	Methods		Case	Control
Arg194Trp	Huang [18]	2007	Asian	China	539	800	MA-PCR	Age,resident and medical history	0.35	0.29	Yes
	Farkasova [19]	2008	Caucasian	Slovakia	17	30	PCR-RFLP	_	_	_	_
	Wang [23]	2010	Asian	China	123	175	PCR-RFLP	Age and medical history	0.28	0.19	Yes
	Settheetham-Ishida [20]	2011	Asian	Thailand	111	118	PCR-RFLP	Medicalhistory	0.30	0.23	No
	Barbisan [21]	2011	Latin America	Argentina	103	114	PCR-RFLP	Age	0.14	0.09	No
Arg280His	Huang [18]	2007	Asian	China	539	800	MA-PCR	Age, residentand medicalhistory	0.12	0.12	Yes
	Wang [23]	2010	Asian	China	123	175	PCR-RFLP	Age andmedical history	0.14	0.10	No
Arg399Glu	Niwa [17]	2005	Asian	Japan	131	320	PCR-RFLP	Age, medical history and smoking	0.29	0.25	Yes
	Huang [18]	2007	Asian	China	539	800	MA-PCR	Age, residentand medicalhistory	0.28	0.19	Yes
	Hong [25]	2008	Asian	China	72	176	Taqman	Age, race, relationship, medical history and sex history	0.26	0.22	Yes
	Farkasova [19]	2008	Caucasian	Slovakia	18	30	PCR-RFLP	_	_	_	_
	Jiang [24]	2009	Asian	China	436	503	PCR-RFLP	Medical history	0.27	0.27	Yes
	Xiao [26]	2010	Asian	China	162	183	PCR-RFLP	Age and medical history	0.27	0.30	Yes
	Settheetham-Ishida [20]	2011	Asian	Thailand	111	118	PCR-RFLP	Medical history	0.22	0.23	Yes
	Barbisan [21]	2011	Latin America	Argentina	103	114	PCR-RFLP	Age	0.33	0.42	Yes
	Roszak [22]	2011	Caucasian	Poland	189	308	PCR-RFLP	Age	0.47	0.37	Yes

PCR-RFLP, polymerase chain reaction - restriction fragment length polymorphism; MA-PCR, mismatch amplification - polymerase chain reaction; MAF, minor allele frequency; HWE, Hardy– Weinberg equilibrium in controls.