Wenzl 2015.

Methods	Randmized, double‐blind, placebo‐controlled withdrawal trial (N = 52)
Participants	CD patients in stable clinical remission (CDAI < 150) on azathioprine for > 4 years
Interventions	1:1 randomization ratio Group 1: placebo (n = 26) Group 2: azathioprine at dose prior to study entry (n = 26) Follow‐up duration: 24 months
Outcomes	Primary outcome: Time interval between first intake of the study drug and disease relapse Secondary outcomes: Disease activity (CDAI), quality of life, and laboratory parameters associated with active disease (CRP, serum hemoglobin, serum albumin, and platelet count)
Notes	Slow recruitment led to premature cessation of the study
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Randomization tables were used according to a 1:1 ratio
Allocation concealment (selection bias)	Low risk	Centralized randomization was performed
Blinding of participants and personnel (performance bias) All outcomes	Low risk	Double‐blind: medicine was provided in identical‐appearing tablets
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Not adequately described
Incomplete outcome data (attrition bias) All outcomes	Low risk	Drop‐outs were balanced across treatment groups 19/26 in the azathioprine group completed the study compared to 23/26 in the placebo group
Selective reporting (reporting bias)	Low risk	All expected outcomes were reported
Other bias	Unclear risk	Premature stopping of the trial due to slow enrolment.