McKenna 2018.

Study characteristics
Methods	Retrospective cohort. Study period: 2007 to 2017
Participants	Country: USA. CD patients who underwent ileocolic resection with primary anastomosis. Patients who underwent ileocolic resection with primary anastomosis and diverting loop ileostomy were excluded
Interventions	1. Preoperative steroids (n= 37) 2. Preoperative immunomodulators (n =57) 3. Preoperative anti‐TNF therapy (n= 322) within 12 weeks of surgery 4. No preoperative steroids (n= 584) 5. No preoperative immunomodulators (n= 564) 6. No preoperative anti‐TNF therapy (n= 299)
Outcomes	Intraabdominal sepsis within 30 days of surgery
Notes	NOS low risk of bias overall Adjusted ORs for preoperative steroids, immunomodulators, and anti‐TNF therapy were obtained from multivariate regression model.
Risk of bias
Bias	Authors' judgement	Support for judgement
Representativeness of the exposed cohort	Low risk	CD patients who underwent ileocolic resection with primary anastomosis from 2007 to 2017
Selection of the non exposed cohort	Low risk	Both groups obtained from the same hospital and time period
Ascertainment of exposure	Low risk	Medical charts were reviewed
Demonstration that outcome of interest was not present at start of study	High risk	61 patients had an abscess at the time of surgery
Comparability of cohorts (Controlled for critical factor/other medications)	Low risk	Controlled for other medications (corticosteroids, immunomodulators, anti‐TNF)
Comparability of cohorts (Controlled for additional factor)	Low risk	Controlled for previous intestinal resection, tobacco use
Assessment of outcome	Low risk	Medical charts were reviewed
Was follow‐up long enough for outcomes to occur	Low risk	30 days
Adequacy of follow up of cohorts	Unclear risk	No information provided