Table 1:
Risk of bias in the included studies
| Reference | Q1 | Q2 | Q3 | Q4 | Q5 | Q6 | Q7 | Q8 | Q9 | Risk of bias score | Risk of bias |
|---|---|---|---|---|---|---|---|---|---|---|---|
| Genetic data | |||||||||||
| Bhatnagar | No | Yes | Yes | Yes | Yes | Yes | No | Yes | Yes | 7 | Moderate |
| Descriptive / Cross-sectional studies | |||||||||||
| Campbell | No | Yes | Yes | Yes | Yes | NA | No | Yes | Yes | 6 | Moderate |
| Desai | No | No | No | Yes | Yes | NA | No | Yes | Yes | 4 | High |
| Johnson | No | Yes | Yes | Yes | Yes | NA | No | Yes | Yes | 6 | Moderate |
| Strumph | No | Yes | Yes | Yes | Yes | NA | No | Yes | Yes | 6 | Moderate |
| Lamarre | No | Yes | Yes | Yes | Yes | NA | No | Yes | Yes | 6 | Moderate |
| Lemonne | No | Yes | Yes | Yes | Yes | NA | No | Yes | Yes | 6 | Moderate |
| Oguanobi | No | No | Yes | Yes | Yes | NA | No | Yes | Yes | 5 | High |
| Pegelow | No | Yes | Yes | Yes | Yes | NA | No | Yes | Yes | 6 | Moderate |
| Pikilidou | No | Yes | Yes | Yes | Yes | NA | No | Yes | Yes | 6 | Moderate |
| Cohort / Case control studies | |||||||||||
| Gordeuk | Yes | Yes | Yes | No | Yes | Yes | No | Yes | Yes | 7 | Moderate |
| Grell | No | Yes | Yes | Unclear | Yes | Yes | Unclear | Yes | Yes | 6 | Moderate |
| Homi | No | Yes | Yes | Yes | Yes | Yes | Unclear | Yes | Yes | 7 | Moderate |
| Kuma | Yes | Yes | Yes | Yes | Yes | Yes | Unclear | Yes | Yes | 8 | Low |
| Makubi | No | Yes | Yes | Yes | Yes | Yes | Unclear | Yes | Yes | 7 | Moderate |
| Novelli | Yes | Yes | Yes | Yes | Yes | Yes | Unclear | Yes | Yes | 8 | Low |