Table 3.

Cochrane Risk of Bias Tool for RCTs, applied for Limmathurotsakul et al. [15]

Entry	Judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Quote: “The randomization codes were generated by a computer using a random mixing box” Comment: Probably done
Allocation concealment (selection bias)	Unclear risk	Quote: “Concealed in envelops” Comment: Insufficient details to allow definite judgement: Were the envelops sealed and/or sequentially numbered?
Blinding of participants and personnel (performance bias)	High risk	Comment: No blinding mentioned in terms of allocated interventions (the group of patients), and the lack of blinding is likely to influence the outcomes
Blinding of outcome assessment (detection bias) (patient-reported outcomes)	Unclear risk	Quote: “The concealed randomization code was opened by an investigator who was blinded to the treatment results” Comment: Probably referring to the treatment results of the biliary drainage and not the outcomes of the study
Blinding of outcome assessment (detection bias) (mortality)	High risk	Comment: No blinding mentioned in terms of outcome assessment (the group of patients), and the lack of blinding is likely to influence the outcomes
Incomplete outcome data addressed (attrition bias)	Low risk	Comment: No missing outcomes reported. Probably true, especially with the low patient number
Selective reporting (reporting bias)	High risk	Comment: An outcome listed in methods is not described in detail: the overall morbidity and mortality related to acute cholangitis