Table 1. Main characteristics of studies included in the meta-analysis.

Reference	Year	Country	Ethnicity	Control source	Genotyping methods	Quality score
de Jonge et al. [23]	2009	Netherlands	Caucasian	PB	PCR-RFLP	5
Gast et al. [24]	2007	Germany	Caucasian	PB	Allelic discrimination	8
Kamel et al. [25]	2007	Egypt	Caucasian	PB	PCR-RFLP	6
Lautner-Csorba et al. [26]	2013	Hungary	Caucasian	HB	MassARRAY	7
Lightfoot et al. [27]	2010	U.K.	Caucasian	PB	TaqMan Assay	9
Metayer et al. [28]	2011	U.S.A.	Caucasian	PB	GoldenGate Assay	8
Milne et al. [29]	2015	Australia	Caucasian	PB	PCR-RFLP	9
Petra et al. [30]	2007	Slovenia	Caucasian	PB	PCR-RFLP	5
Rahimi et al. [31]	2012	Iran	Caucasian	PB	PCR-RFLP	7
Nikbakht et al. [32]	2012	India	Asian	PB	PCR-RFLP	9

Abbreviations: HB, hospital-based; PB, population-based; PCR, polymerase chain reaction; RFLP, restriction fragment length polymorphism.