Table 1.
Characteristics of the studies included in the meta-analysis
| First author | Year | Country | Ethnicity | Source of controls | Genotyping method | Number (case/control) | HWE | Quality assessment score | Published language |
|---|---|---|---|---|---|---|---|---|---|
| Bo [37] | 2010 | China | Asian | HB | PCR-RFLP | 208/190 | 0.389403209 | 7 | English |
| Canedo [36] | 2008 | Portugal | European | PB | Taq Man-PCR | 333/693 | 0.459719109 | 8 | English |
| Crusius [35] | 2008 | Caucasia | European | PB | Real-time | 236/1139 | 0.705567725 | 8 | English |
| de Oliveira [34] | 2015 | Brazil | European | HB | PCR-RFLP | 207/240 | 0.059480986 | 7 | English |
| Felipe [33] | 2012 | Brazil | European | PB | PCR-RFLP | 104/196 | 0.065528611 | 8 | English |
| Garza-Gonzalez [32] | 2007 | Mexico | European | HB | ARMS-PCR | 78/189 | 0.538816094 | 7 | English |
| Kamali-Sarvestani [31] | 2006 | Iran | Asian | HB | ASO-PCR | 19/153 | 0.797575578 | 7 | English |
| Kamangar [30] | 2006 | Finland | European | PB | TaqMan-PCR | 112/207 | 0.054934096 | 8 | English |
| Kang [29] | 2009 | Korea | Asian | PB | PCR-RFLP | 334/322 | 0.22569954 | 8 | English |
| Ko [28] | 2009 | Korea | Asian | PB | Snapshot | 81/308 | 0.155354832 | 8 | English |
| Lee [27] | 2005 | Taiwan | Asian | HB | PCR-RFLP | 470/308 | 0.14303682 | 7 | English |
| Liu [12] | 2009 | China | Asian | HB | Taq Man-PCR | 138/137 | 0.145093518 | 7 | Chinese |
| Lu [26] | 2005 | China | Asian | PB | PCR-DHPLC | 250/300 | 0.515848398 | 8 | English |
| Ohyauchi [25] | 2005 | Japan | Asian | HB | Direct | 212/346 | 0.549317592 | 7 | English |
| Pan [24] | 2014 | China | Asian | HB | SBE | 308/308 | 0.715713139 | 7 | English |
| Qadri [23] | 2014 | India | Asian | PB | PCR-CTPP | 130/200 | 0.066109789 | 8 | English |
| Ramis [22] | 2015 | Brazil | European | PB | PCR-RFLP | 9/38 | 0.691258974 | 8 | English |
| Savage [21] | 2004 | China | Asian | PB | SBE | 88/429 | 0.884813104 | 8 | English |
| Savage [20] | 2006 | Poland | European | PB | Taqman or MGB Eclipse | 287/428 | 0.391465014 | 8 | English |
| Shirai [19] | 2006 | Japan | Asian | HB | PCR-RFLP | 181/468 | 0.830460367 | 7 | English |
| Song [18] | 2009 | China | Asian | HB | PCR-RFLP | 125/140 | 0.720157181 | 7 | English |
| Taguchi [17] | 2005 | Japan | Asian | HB | PCR-RFLP | 396/252 | 0.994013656 | 7 | English |
| Vinagre [16] | 2011 | Brazil | European | HB | PCR-RFLP | 102/103 | 0.150502334 | 7 | English |
| Ye [15] | 2009 | Korea | Asian | HB | PCR-RFLP | 153/206 | 0.552934095 | 7 | English |
| Zeng [14] | 2005 | China | Asian | PB | PCR-RDB | 206/196 | 0.02187681 | 8 | Chinese |
| Zhang [13] | 2010 | China | Asian | PB | PCR-RFLP | 519/504 | 0.75413968 | 8 | English |
HWE: Hardy-Weinberg equilibrium; PB: population based; HB: hospital-based; PCR: polymerase chain reaction; RFLP: restriction fragment length polymorphism; SBE, single base extension; PCR-RDB, polymerase chain reaction-reverse dot blot. DHPLC: PCR-based denaturing high-performance liquid chromatography; Direct: Direct sequence analysis of polymerase chain reaction; ASO: oligonucleotide allele specific polymerase chain reaction; MGB Eclipse: MGB Eclipse Assay polymerase chain reaction method; ARMS: Amplification refractory mutation system polymerase chain reaction; Snapshot: the Snapshot assay which provides detection of certain SNPs. CTPP: confronting two-pair primers. The quality of studies included in this meta-analysis was assessed using Newcastle-Ottawa scale, which graded the quality of a study from 0 to 10 points. Articles exceeding 6 points were considered as high quality.