Table 2.

Bias risks of the included RCT

Study, year	Domain 1	Domain 2	Domain 3	Domain 4	Domain 5	Domain 6	Domain 7
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

¹Random sequence generation (selection bias)

²allocation concealment (selection bias)

³blinding of participants and personnel (performance bias)

⁴blinding of outcome assessment (detection bias) (patient-reported outcome)

⁵blinding of outcome assessment (detection bias) (all-cause main outcome)

⁶incomplete outcome data (attrition data)

⁷selective reporting (reporting bias)