Risk of bias domain | Roncin et al, 15 1996 | Gertsch et al, 16 2002 | Gertsch et al, 17 2004 | Chow et al, 18 2005 | Moraga et al, 13 2007 | Leadbetter et al, 19 2009 |
Random-sequence generation (selection bias) | Unclear | Unclear | Low | Low | Low | Low |
Allocation concealment (selection bias) | Unclear | Low | Low | Low | Unclear | Low |
Blinding of participants (performance bias) | High | Low | Low | Low | High | Low |
Blinding of outcome assessment (detection bias) | High | Low | Low | Low | High | Low |
Incomplete outcome data (attrition bias) | High | High | Low | Low | Low | Low |
Selective outcome reporting (reporting bias) | Low | Low | Low | Low | Low | Low |
Other source of bias | High | Low | High | Low | High | Low |
Overall risk of bias | High | High | Low | Low | High | Low |