Table 2. Distribution of genotypes and alleles in the individual study.

First author,published year	Genotype							Gene allele				Allele frequency		HWE for controls
	Case			Control				Case		Control		Case	Control
	CC	CT	TT	CC	CT	TT	Total	C	T	C	T	C	C	x2	P
Li Y,2007	45	104	11	12	66	14	252	194	126	90	94	0.61	0.49	17.45	2.956E-05
WangCP, 2009	121	257	96	35	118	72	699	499	449	188	262	0.53	0.42	1.37	0.242
TianCX, 2010	96	116	36	42	102	62	454	308	188	186	226	0.62	0.45	1.6788E-05	0.997
Yan JC,2010	95	216	88	26	87	50	562	406	392	139	187	0.51	0.43	1.35	0.245
WangM,2011	53	87	20	41	96	43	340	193	127	178	182	0.60	0.49	0.80	0.370
Ma Y,2013	54	196	36	112	173	51	622	304	268	397	275	0.53	0.59	1.41	0.234
ZhangBK,2013	110	216	76	243	335	115	1095	436	368	821	565	0.54	0.59	6.38E-04	0.980

Abbreviation: HWE, Hardy-Weinberg equilibrium.