Table 1.

Characteristics of the studies included in the meta-analysis

First author	Year	Country	Ethnicity	Study design	Genotyping method	Source of control	Total sample size(case/control)	SNP No.	NOS score
Cunningham	2003	Australia	Caucasian	CC	SSOP	PB	109/164	2	8
Lech-Maranda	2004	France	Caucasian	CC	PCR-RFLP	PB	199/112	2;3;4	8
Guzowski	2005	USA	Mix	CC	Taqman	PB	17/25	2;3;4	8
Berglund	2005	Sweden	Caucasian	CC	NR	PB	244/195	2	6
Wang	2006	USA	Mix	CC	Taqman	PB	1133/936	1	9
Lan	2006	USA	Mix	CC	Taqman	Female	510/597	1;2;3	7
Nieters	2006	Germany	Caucasian	CC	Taqman	PB	507/661	1	9
Rothman	2006a	Canada	Caucasian	CC	Taqman	PB	85/349	1	8
	2006b	Italy	Caucasian	CC	Taqman	PB	59/112	1	8
	2006c	Spain	Caucasian	CC	Taqman	HB	77/554	1	7
	2006d	USA	Caucasian	CC	Taqman	PB	93/677	1	8
	2006e	UK	Caucasian	CC	Taqman	PB	262/459	1	8
Purdue	2007	USA	Caucasian	CC	Taqman	PB	524/475	1;2;3;4	9
Lech-Maranda	2007	France	Caucasian	CC	PCR-RFLP	PB	175/112	2;3;4	8
Kube	2008	Germany	Caucasian	CC	Taqman	HB	500/236	1;2;4	7
Maria	2008	Italy	Caucasian	CC	Taqman	PB	39/112	1;2	7
Liang	2009	USA	Caucasian	CC	OPA	PB	39/102	1	7
Fernberg	2010	Sweden	Caucasian	CC	MassArray	PB	2312/1838	1	9
Zhang	2012	China	Asian	CC	Taqman	PB	514/557	4	8
Lech-Maranda	2013	Poland	Caucasian	CC	Taqman	PB	290/192	1;2	8
Talaat	2014	Egypt	Caucasian	CC	SSP-PCR	PB	100/119	2;3	7

CC: case-control; SNP: single-nucleotide polymorphisms; SNP No.1: -3575 T>A (rs1800890); 2: -1082 A>G (rs1800896); 3: -819 T>C (rs1800871); 4: -592 A>C (rs1800872); PB: population based; HB: hospital based; NR: not reported; PCR-RFLP: polymerase chain reaction and restriction fragment length polymorphism; OPA: Oligo Pool Assay; SSOP: sequence specific oligo probing; SSC-PCR: sequence-specific primers polymerase chain reaction; NOS: the Newcastle-Ottawa Scale.