| Study | Country/Area | Ethnicity | Genotyping Method | Diagnostic Criteria | Case (n) | Control (n) |
| Zhang et al., 1997 [32] | Japan | Asian | PCR-SSCP | DSM-IV | 51 | 150 |
| Frisch et al., 1999 [33] | Israel | Caucasian | PCR-Msp I | DSM-IV | 99 | 172 |
| Tsai et al., 1999 [34] | Taiwan (China) | Asian | PCR-HpaII | DSM-IV | 79 | 96 |
| Bondy et al., 2000 [35] | Germany | Caucasian | PCR-Msp I | DSM-IV | 84 | 125 |
| Arias et al., 2001 [15] | Spain | Caucasian | PCR-Msp I | DSM-IV | 159 | 164 |
| Minov et al., 2001 [36] | Germany | Caucasian | PCR-Msp I | DSM-IV | 172 | 121 |
| Correa et al., 2002 [37] | Brazil | Other | PCR-Hpa II | DSM-IV | 78 | 52 |
| Oswald et al., 2003 [38] | Europe | Caucasian | PCR-Msp I | DSM-IIIR | 142 | 142 |
| Terayama et al., 2003 [23] | Japan | Asian | PCR-Msp I | DSM-IV | 39 | 112 |
| Illi et al., 2009 [21] | Finland | Caucasian | Taqman Assay | DSM-IV | 86 | 395 |
| Kishi et al., 2009 [22] | Japan | Asian | Taqman Assay | DSM-IV | 325 | 802 |
| Yusup et al., 2013 [31] | China-Uighur (China) | Other | PCR-Msp I | CCMD-3 | 195 | 50 |
| Guo et al., 2014 [39] | China | Asian | PCR-Msp I | DSM-IV | 72 | 70 |
| Zhang et al., 2016 [25] | China | Asian | MALDI-TOF | DSM-IV | 558 | 842 |
| Basu et al., 2019 [20] | India | Other | SEQUENOME | DSM-IV | 80 | 80 |