Table 1. Characteristics of the studies included in the meta-analysis.
| First author | Year | Country | Ethnicity | Genotyping medthod | Source of control |
Total sample size (case/control) | SNP No. |
|---|---|---|---|---|---|---|---|
| Prokunina-1[10] | 2002 | Norway | Caucasian | PCR-RFLP | Population | 32/32 | 3,4,5 |
| Prokunina-2 | 2002 | Sweden | Caucasian | PCR-RFLP | Population | 263/235 | 3,4,5 |
| Prokunina-3 | 2002 | America | Caucasian | PCR-RFLP | Population | 145/80 | 3,4,5 |
| Prokunina-4 | 2002 | Mexico | Mixed | PCR-RFLP | Population | 402/149 | 3,4,5 |
| Prokunina-5 | 2002 | America | African | PCR-RFLP | Population | 80/18 | 3,4,5 |
| Ferreiros-Vidal[7] | 2004 | Spain | Caucasian | PCR-RFLP | Population | 518/800 | 3 |
| Nielsen [23] | 2004 | Denmark | Caucasian | sequencing | Population | 95/155 | 3,4,5 |
| Sanghera-1 [22] | 2004 | America | Caucasian | PCR-RFLP | Population | 276/359 | 3 |
| Sanghera-2 | 2004 | America | African | PCR-RFLP | Population | 35/31 | 3 |
| Johansson [24] | 2005 | Sweden | Caucasian | TaqMan | Population | 260/670 | 3 |
| Wang20 | 2006 | Taiwan | Asian | PCR-RFLP | Hospital | 109/100 | 1,2,3,4,5 |
| Ferreiros-Vidal-1 [21] | 2007 | Germany | Caucasian | PCR-RFLP | Population | 101/100 | 3 |
| Ferreiros-Vidal-2 | 2007 | Czech R | Caucasian | PCR-RFLP | Population | 101/100 | 3 |
| Ferreiros-Vidal-3 | 2007 | Greece | Caucasian | PCR-RFLP | Population | 198/380 | 3 |
| Ferreiros-Vidal-4 | 2007 | Hungary | Caucasian | PCR-RFLP | Population | 93/99 | 3 |
| Ferreiros-Vidal-5 | 2007 | Italy | Caucasian | PCR-RFLP | Population | 86/218 | 3 |
| Ferreiros-Vidal-6 | 2007 | Italy | Caucasian | PCR-RFLP | Population | 128/211 | 3 |
| Ferreiros-Vidal-7 | 2007 | Italy | Caucasian | PCR-RFLP | Population | 76/102 | 3 |
| Velazquez-Cruz [11] | 2007 | Mexico | Mixed | TaqMan | Population | 250/355 | 3,4,5 |
| Kong [18] | 2008 | China | Asian | PCR-RFLP | Hospital | 164/163 | 2 |
| Kong [19] | 2008 | China | Asian | PCR-RFLP | Hospital | 132/160 | 4,5 |
| Mostowska [12] | 2008 | Poland | Caucasian | PCR-RFLP | Population | 102/140 | 2,3,5 |
| Bertsias [17] | 2009 | Greece | Caucasian | PCR-RFLP | Population | 289/256 | 3 |
| Peng [16] | 2010 | China | Asian | PCR-RFLP | Hospital | 159/159 | 2,4,5 |
| Chua-1[13] | 2015 | China | Asian | TaqMan | Population | 115/115 | 1,3,4,5 |
| Chua-2 | 2015 | Malaysia | Asian | TaqMan | Population | 70/70 | 1,3,4,5 |
| Chua-3 | 2015 | India | Asian | TaqMan | Population | 15/15 | 1,3,4,5 |
| Mahmoudi [14] | 2015 | Iran | Asian | PCR-RFLP | Population | 50/202 | 1,3 |
CC: case-control, PCR: polymerase chain reaction, RFLP: restriction fragment length polymorphism. SNP: single-nucleotide polymorphisms; SNP No.1: rs 36084323 G > A (PD1.1); 2: rs 34819629 G > A (PD1.2); 3: rs 11568821 G>A (PD1.3); 4: rs 2227981 C > T (PD1.5); 5: rs 10204525 G > A (PD1.6)