Table 2. Bias risks of the included RCT
Study, year	Domain1	Domain2	Domain3	Domain4	Domain5	Domain6	Domain7
Moraloglu et al., 2010	High	High	Low	unknown	Low	Low	unknown
Ng et al., 2014	Unknown	Low	Low	unknown	Low	Low	Low
He et al., 2016a	Low	Low	unknown	unknown	Low	Low	Low
Hebisha et al., 2016	Unknown	unknown	unknown	unknown	Low	Low	unknown
1: Random sequence generation (selection bias) 2: allocation concealment (selection bias) 3: blinding of participants and personnel (performance bias) 4: blinding of outcome assessment (detection bias) (patient-reported outcome) 5: blinding of outcome assessment (detection bias) (all-cause main outcome) 6: incomplete outcome data (attrition data) 7: selective reporting (reporting bias)