Table 3

Risk of bias summary

Study, year (reference)Random sequence generationAllocation concealmentBlinding of participants and personnelBlinding of outcome assessmentIncomplete outcome dataSelective reporting
Anderson et al, 198735??++??
Chan et al, 200739++++??
Farci et al, 200443++++??
Krogsgaard, 199828??++−?
Liaw et al, 200427++++++
Mazzella et al, 199953??+++?
Robson et al, 199256??++??
Waked et al, 199062??++??

  • +, Low risk of bias; −high risk of bias; ?, unknown risk of bias.