| Study | Reason for exclusion |
|---|---|
| Bertino 2009 | This is a case‐control study |
| Cobb 2004 | This is a case‐control study |
| Malhotra 1992 | This is a prospective observational study |
| Mihatsch 2002 | This is a prospective observational study |
| Riskin 2017 | This is a case‐control study |
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