Table-II.

Characteristics of studies of MTHFR C677T polymorphism and ESCC

Study ID	County	Control source	Case	Control	Cases			Controls			P HWE	Quality score
					CC	CT	TT	CC	CT	TT
Chen Y 2009 (16)	China	Hospital	103	181	11	49	43	45	85	51	0.42	10
Feng CW 2006 (17)	China	Population	275	315	51	105	119	74	143	98	0.12	8
Zhao PC 2011 (18)	China	Hospital	155	310	68	74	13	179	120	11	0.09	9
Li DQ 2011 (19)	China	Hospital	226	246	112	113	45	95	82	85	<0.1	9
Li DQ 2008 (20)	China	Population	126	169	22	52	52	41	62	66	<0.1	10
Wang YM 2007(21)	China	Population	584	540	73	263	248	119	234	187	<0.1	11
Qin JM 2008 (22)	China	Population	120	204	60	53	7	170	59	11	0.06	11
He YT 2007 (23)	China	Population	584	540	73	263	248	119	234	187	<0.1	10
Song C 2001 (9)	China	Population	240	360	29	118	93	126	172	62	0.8	11
Wang LD 2005 (24)	China	Population	275	315	51	105	119	74	143	98	0.12	10
Yang CX 2005 (12)	Japan	Hospital	165	493	63	82	20	186	227	80	0.45	9
Zhang J 2004 (25)	German	Population	241	256	94	116	31	107	115	34	0.72	10
Zhang J 2004 (25)	China	Population	189	141	16	93	80	25	54	62	<0.1	10
Kureshi N 2004 (26)	Pakistan	Population	34	54	22	12	0	32	18	4	0.52	8
Zhang JH 2003(27)	China	Population	198	141	16	93	89	25	54	62	<0.1	7
Stolzenberg RZ 2003 (11)	China	Population	129	398	23	58	48	65	209	124	0.14	8
Miao XP 2002 (28)	China	Population	217	468	47	107	63	151	217	100	0.18	12
Umar M 2010 (29)	India	Hospital	208	223	155	48	5	155	63	5	0.63	13
Total			4239	5576	1008	1856	1375	1829	2353	1393
Results of meta-analysis (Random effect model), OR(95% CI)			CT vs CC		1.47(1.32-1.63), P for heterogeneity: <0.05
			TT vs CC		1.69(1.49-1.91), P for heterogeneity: <0.05