Table 1. Characteristics of the included studies.
| Study | Year | Country | Ethnicity | Diseases | Genotyping | Source of controls | Case | Control | HWE | ||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| TT | TG | GG | TT | TG | GG | ||||||||
| Pouladian [35] | 2017 | Iran | Asian | MS | RFLP | HB | 102 | 34 | 4 | 116 | 21 | 1 | 0.963 |
| Inoue [22] | 2017 | Japan | Asian | AITDs | RFLP | HB | 273 | 14 | 0 | 66 | 4 | 0 | 0.806 |
| Wang [27] | 2014 | China | Asian | AS | RFLP | HB | 262 | 20 | 0 | 279 | 19 | 0 | 0.570 |
| Liang [24] | 2012 | China | Asian | GD | PCR-SSP | PB | 172 | 10 | 0 | 147 | 3 | 0 | 0.902 |
| Xu [28] | 2011 | China(Hui) | Asian | RA | PCR-SSP | PB | 198 | 28 | 0 | 224 | 7 | 0 | 0.815 |
| Xu [28] | 2011 | China | Asian | RA | PCR-SSP | PB | 90 | 13 | 0 | 103 | 5 | 0 | 0.806 |
| Song [26] | 2011 | China | Asian | RA | TaqMan | HB | 335 | 31 | 0 | 365 | 24 | 0 | 0.530 |
| Radwan [34] | 2011 | Egypt | African | ITP | RFLP | PB | 62 | 35 | 0 | 131 | 68 | 9 | 0.963 |
| Du [21] | 2009 | China | Asian | ITP | RFLP | HB | 178 | 9 | 0 | 120 | 3 | 0 | 0.891 |
| Chas [20] | 2004 | Korea | Asian | RA | SBE | PB | 203 | 93 | 0 | 256 | 63 | 0 | 0.050 |
Abbreviations: AITD, autoimmune thyroid disease; AS, ankylosing spondylitis; GD, Graves’ disease; HB, hospital-based; HWE, Hardy–Weinberg equilibrium of controls; ITP, idiopathic thrombocytopenic purpura; PB, population-based; PCR-SSP, polymerase chain reaction with sequence specific primers; RA, rheumatoid arthritis; RFLP, restriction fragment length polymorphism.