De Cruz 2015.

Study characteristics
Methods	Multicentre randomised‐controlled trial conducted in Australia and New Zealand (17 centres) between Oct 13, 2009, and Sept 28, 2011. Trial duration: 18 months
Participants	Adults undergoing bowel resection due to Crohn disease (resection of all macroscopic disease) with an endoscopically accessible anastomosis. Participants with high and low risk of postoperative recurrence were included. High risk was defined as having one or more of the following factors: Smoking (any number of cigarettes at study entry) Perforating disease (abscess, enteric fistula, or free perforation) Previous resection. One hundred eighty‐four participants were initially randomised, but 10 participants were excluded from the analysis after randomisation, because they did not receive the allocated management (four in the control group, six in the intervention group). Control group 52 participants (44 high risk, 8 low risk) Intervention group 122 participants (101 high risk, 21 low risk)
Interventions	All participants received a tailored preventive therapy immediately after surgery: Low‐risk participants: no treatment High‐risk participants: azathioprine (2.0 mg/kg per day) or 6‐mercaptopurine (1.5 mg/kg per day) Control group No colonoscopy. Intensification of therapy only in case of clinical recurrence. Intervention group Colonoscopy at 6 months after surgery. Intensification of prophylactic‐therapy in case of endoscopic recurrence. Intensification therapy Low‐risk participants: azathioprine (2.0 mg/kg per day) or 6‐mercaptopurine (1.5 mg/kg per day) High‐risk participants: adalimumab (160 mg, 80 mg two weeks later, then 40 mg every two weeks)
Outcomes	Primary outcome Endoscopic recurrence (Rutgeerts' score ≥ i2) Secondary outcomes Clinical recurrence (CDAI> 150 or 200 points) Surgical recurrence
Notes	This study was unblinded, however, the outcome assessment of endoscopic recurrence was blinded (photographs of endoscopic findings were scored by two investigators masked to participant’s identity and treatment). The authors received funding to conduct this study from pharmaceuticals, government and private funds (philanthropy). The authors declare that the funders of the study had no role in the design of the study, data collection or analysis, interpretation of data, writing of the report, or in the decision to submit the paper for publication. The following authors declared these potential conflicts of interest. PDC has received travel grant support from AbbVie and Schering‐Plough and has been a speaker for Janssen. MAK has acted as an adviser to AbbVie and Janssen, has received research support from AbbVie, and has acted as a speaker at symposiums sponsored by AbbVie and Janssen. ALH has received an educational grant from AbbVie. DL has served on advisory boards and received research grants from AbbVie. ICL has been on an advisory board, been a speaker, and received research support from AbbVie and Janssen. JMA has been on an advisory board, been a speaker, and received research support from AbbVie and Janssen. PAB has been on advisory boards, for Janssen and Abbvie, and has received research funding and travel sponsorship from both AbbVie and Janssen. PRG has received consulting fees from AbbVie, Janssen, Ferring, and Takeda; research support from AbbVie, Janssen, Ferring, and Falk Pharm; and payments for lectures from AbbVie, Janssen, Ferring, AstraZeneca, and Pfizer. RWL has served on advisory boards for AbbVie, Janssen, Ferring, and Takeda and received a research grant from Shire. RBG has been on an advisory board for AbbVie and Janssen, a speaker for AbbVie and Janssen, and held research, educational and travel grants from AbbVie and Janssen. FAM has been on an advisory board to Janssen, has received travel grants from AbbVie, and has received clinical research support from Janssen, AbbVie, and MSD. WS has been on an advisory board for AbbVie. SJBe has received travel assistance from AbbVie and has been a speaker and educational consultant for Abbvie and Janssen and has received research support from Shire. WRC has been a speaker for AbbVie and received travel assistance from Abbvie. The following authors declared no conflicts of interest: KJR, EOK, AG, LP, THF, GR‐S, MS, HD, IK, MJJ, RW, PRE, SJBr, and PVD.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Computer‐generated randomisation, in blocks of 3 in a 2:1 ratio.
Allocation concealment (selection bias)	Low risk	Computer‐generated with block randomisation undertaken for each centre. The allocation list was maintained centrally
Blinding of participants and personnel (performance bias) All outcomes	High risk	Open‐label study. Participants, personnel and endoscopists were unblinded.
Blinding of outcome assessment (detection bias) Clinical recurrence	High risk	Open‐label study. CDAI score has subjective items that are assessed by participants.
Blinding of outcome assessment (detection bias) Endoscopic recurrence	Low risk	The assessment was carried out using photographs. Two masked investigators scored the pictures.
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	All withdrawals were reported with reasons, were balanced across groups and the analysis was conducted according to ITT principle. Despite this, 32.1% of participants dropped out the study. All withdrawals were included in the final analysis as participants with endoscopic and clinical recurrence.It is not clear the real impact in the final estimate of the effect (this could be inaccurate) Ten participants were excluded from the analysis after randomisation, because they did not receive the allocated management.
Selective reporting (reporting bias)	Low risk	Protocol outcomes were the same as final report. ClinicalTrials.gov number NCT00989560
Other bias	Low risk	Comment: No other major risk of bias was noticed