Supplementary table 2. Risk of bias assessment for individual studies using the Risk of Bias in non-randomised studies of interventions tool (ROBINS-I). Each domain was classified as low risk, moderate risk, serious risk, and critical risk or no information on which to base the judgement. An overall bias assessment was performed using the recommended scale[1].

Risk of Biases
Author / Confounding / Participant selection / Classification of interventions / Departures from intended interventions / Missing data / Measurement of outcomes / Selection of the reported result / Overall
Campillo[28] / Serious / Serious / Serious / Moderate / Serious / Moderate / Moderate / Serious
Cerqueira[29] / Moderate / Low / Serious / Moderate / Moderate / Moderate / Moderate / Serious
Chung[25] / Low / Serious / Moderate / Low / Serious / Low / Low / Serious
Georgopoulos[30] / Moderate / Low / Low / Moderate / Low / Low / Low / Moderate
Gisbert[22] / Low / Low / Low / Moderate / Low / Low / Low / Low
Gisbert[36] / Low / Low / Low / Low / Low / Low / Low / Low
Gisbert[37] / Low / Low / Low / Low / Low / Low / Low / Low
Hsu[24] / Low / Low / Serious / Low / Low / Low / Low / Serious
Kang[26] / Serious / Moderate / Moderate / Moderate / Low / Moderate / Serious / Serious
Lim[27] / Moderate / Moderate / Serious / Low / Moderate / Low / Serious / Serious
Liou[39] / Moderate / Low / Low / Low / Low / Low / Moderate / Moderate
Manfredi[33] / Moderate / Low / Low / Low / Low / Low / Low / Low
Perna[34] / Moderate / Low / Low / Low / Low / Low / Low / Low
Pontone[35] / Moderate / Low / Low / Low / Low / Low / Low / Low
Zullo[32] / Low / Low / Low / Low / Low / Low / Low / Low
Zullo[31] / Low / Moderate / Low / Low / Low / Low / Low / Low

1

[1] Sterne JAC, Higgins JPT, Elbers RG, Reeves BC and the development group for ROBINS-I. Risk Of Bias In Non-randomized Studies of Interventions (ROBINS-I): detailed guidance, updated 12 October 2016. Available from http://www.riskofbias.info [accessed 09-Feb-2017]