Table 1. Main characteristics and methodological quality of all eligible studies.

First author [Ref]	Year	Country	Ethnicity	Sample size		Gender (male/female)		Age (years)		Marker	Detection method	NOS score
				Case	Control	Case	Control	Case	Control
Pimentel-Nunes P [13]	2013	Portugal	Caucasian	193	278	123/70	176/102	62.0±7.0	56.0±4.0	299 A>G	PCR-RFLP	7
Omrane I [10]	2013	Tunisia	African	100	140	53/47	45/95	58.2±14.4	56.2±15.7	299 A>G	Direct sequencing	8
										399 C>T	Direct sequencing	8
Dai Q [21]	2012	China	Asian	268	268	-	-	-	-	299 A>G	PCR-RFLP	6
Yang GG [22]	2011	China	Asian	102	87	64/38	52/35	52	50	299 A>G	Direct sequencing	6
										399 C>T	Direct sequencing	6
Boraska Jelavic T [17]	2006	Croatia	Caucasian	89	88	61/28	61/67	61.5±9.5	61.5±9.5	299 A>G	PCR-RFLP	6
										399 C>T	PCR-RFLP	6
Davoodi H [14]	2011	Malaysia	Asian	60	50	30/30	25/25	30∼50	30∼50	299 A>G	PCR-RFLP	6
										399 C>T	PCR-RFLP	6
Nihon-Yanagi Y [28]	2012	Japan	Asian	50	50	22/28		68 (52∼90)		mRNA	RT-PCR	7
Yu YH [30]	2011	China	Asian	62	25	-		-		mRNA	RT-PCR	6
Huang HY [26]	2010	China	Asian	63	63	35/28		-		mRNA	RT-PCR	7
Jin HM [27]	2009	China	Asian	24	24	11/13		67 (35∼86)		mRNA	RT-PCR	8
Tian F [29]	2008	China	Asian	30	30	18/12		64 (51∼82)		mRNA	RT-PCR	8
Hu KF [25]	2013	China	Asian	40	20	27/13		32∼80		Protein	SP	8
Cheng ZL [23]	2012	China	Asian	58	25	38/20		22∼83		Protein	SP	8
Guo YW [24]	2007	China	Asian	70	70	42/28		33∼71		Protein	Flow cytometry	8

Legend: PCR-RFLP - polymerase chain reaction-restriction fragment length polymorphism; NOS - the Newcastle-Ottawa Scale.