Endoscopic retrograde cholangiopancreatography drainage for palliation of malignant hilar biliary obstruction — stent-in-stent or side-by-side? A systematic review and meta-analysis

Table 2 Risk of bias for ROBINS-I

Ref.	D1	D2	D3	D4	D5	D6	D7	Overall
Naitoh et al[30] 2012	Moderate	Moderate	Low	Low	Low	Moderate	Moderate	Moderate
Kim et al[31] 2012	Serious	Serious	Low	Serious	Serious	Serious	Serious	Serious
Law et al[29] 2013	Moderate	Moderate	Low	Low	Moderate	Moderate	Serious	Moderate
Ishigaki et al[32] 2020	Moderate	Moderate	Low	Low	Low	Moderate	Moderate	Moderate

D: Domains; D1: Bias due to confounding; D2: Bias due to selection of participants; D3: Bias in classification of interventions; D4: Bias due to deviations from intended interventions; D5: Bias due to missing data; D6: Bias in measurement of outcomes; D7: Bias in selection of the reported result.