Table 1. Main characteristics of eligible studies in this meta-analysis.

Author names	Years	Areas	Ethnicity	Genotyping method	Cases/controls	Cases			Controls			HWE	Association observed
						CC	CT	TT	CC	CT	TT
Nexo et al. [26]	2003	Denmark	Caucasian	TaqMan	415/414	53	176	186	69	183	162	YES	No risk
Lee et al. [27]	2005	Korea	Asian	MALDI-TOF	705/550	411	257	37	323	187	40	YES	No risk
Yang et al. [28]	2013	China	Asian	TaqMan	461/504	183	166	112	232	184	88	NO	TT genotype showed increased risk
Zhu et al. [29]	2015	China	Asian	PCR-RFLP	101/101	56	41	4	63	33	5	YES	No risk
Gomez-Diaz et al. [30]	2015	Mexico	Mexican-mestizo	TaqMan	71/74	38	28	5	40	27	7	YES	No risk
He et al. [31]	2016	China	Asian	MALDI-TOF	450/430	230	195	25	261	151	18	YES	TT/TC genotype showed increased risk
Pongsavee et al. [32]	2017	Thailand	Asian	TaqMan	151/120	105	33	13	101	9	10	NO	TT/TC genotype showed increased risk

Abbreviation: PCR-RFLP, PCR-restriction fragment length polymorphism.