Table 3 Risk of bias of included studies
Study (year) | Was the allocation sequence adequately generated? | Was allocation adequately concealed? | Was the study adequately protected against contamination? | Was knowledge of the allocated interventions adequately prevented? | Were incomplete outcome data adequately addressed? | Was baseline outcome measurement similar? | Was baseline characteristics similar? | Was the study free from selective outcome reporting? | Overall riska |
|---|---|---|---|---|---|---|---|---|---|
 1. Basheti (2009) | Low | Unclear | Unclear | Unclear | Low | Low | Low | Low | Unclear |
 2. Chalker (2005) | Unclear | Unclear | Low | Unclear | Low | Low | Unclear | Low | Unclear |
 3. Chuc (2002) | Low | Unclear | Low | Low | Low | Low | Unclear | Low | Unclear |
 4. de Almeida Neto (2000) | Unclear | Unclear | Unclear | Unclear | Low | Unclear | Unclear | Low | Unclear |
 5. de Almeida Neto (2000) | Unclear | Unclear | Unclear | Unclear | Low | Unclear | Unclear | Low | Unclear |
 6. Dolovich (2007) | Low | Unclear | Unclear | Low | Low | Unclear | Low | Low | Unclear |
 7. Garcia (1998) | Unclear | Unclear | Low | Low | Low | Unclear | Unclear | Low | Unclear |
 8. Garcia (2003) | Low | Unclear | Low | Low | Low | Unclear | Unclear | Low | Unclear |
 9. Kimberlin (1993) | Unclear | Low | Unclear | Unclear | Low | Unclear | Low | Low | Unclear |
 10. Lalonde (2008) | Low | Low | Low | High | Low | Low | High | Low | High |
 11. Mayer (1998) | Unclear | Unclear | Low | Low | Low | Low | Unclear | Low | Unclear |
 12. Patwardhan (2012) | Low | Low | Low | Unclear | Low | Low | Low | Low | Unclear |
 13. Prokhorov (2010) | Unclear | Unclear | Low | Unclear | Low | Unclear | Low | Low | Unclear |
 14. Reeves (2007) | Low | Unclear | Low | High | Low | Unclear | Low | Low | High |
 15. Sigrist (2002) | Unclear | Unclear | Unclear | Low | Low | Low | Unclear | Low | High |
 16. Sinclair (1998) | High | Unclear | Low | Low | Low | Unclear | Low | Low | Unclear |
 17. Watson (2002) | Low | Unclear | Low | Unclear | Low | Low | Low | Low | Unclear |