| Study | Country/Area | Ethnicity | Genotyping Method | Diagnostic Criteria | Case (n) | Control (n) |
| Bonnier et al., 2002 [29] | France | Caucasian | PCR | DSM-IV | 65 | 142 |
| Terayama et al., 2003 [23] | Japan | Asian | PCR-Msp I | DSM-IV | 39 | 112 |
| Choi et al., 2004 [18] | Korea | Asian | PCR-Msp I | DSM-IV | 189 | 148 |
| Illi et al., 2009 [21] | Finland | Caucasian | Taqman Assay | DSM-IV | 86 | 395 |
| Noskova et al., 2009 [19] | Russia | Caucasian | PCR-Msp I | ICD-10 | 174 | 328 |
| Tencomnao et al., 2010 [30] | Thailand | Asian | PCR-Msp I | DSM-IV | 180 | 183 |
| Yusup et al., 2013 [31] | China-Uighur (China) | Other | PCR-Msp I | CCMD-3 | 195 | 50 |
| 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 |