Colombel 2004.

Study characteristics
Methods	Retrospective cohort. Study period: 1998 to 2001
Participants	Country: USA. CD patients who underwent surgical resection, stricturoplasty, or intestinal bypass. Patients who received cyclosporine, tacrolimus, or investigational therapy within 8 weeks of surgery were excluded. Patients who underwent perianal surgery were also excluded.
Interventions	1. Preoperative infliximab (n= 52) 8 weeks prior to surgery and within 30 days after surgery 2. Preoperative azathioprine/6‐mercatopurine/methotrexate (n= 105) 3. Preoperative moderate/high dose steroids (n= 77) 4. No preoperative infliximab (n= 218) 5. No preoperative azathioprine/6‐mercatopurine/methotrexate (n= 165) 6. Low dose/no preoperative steroids (n=193)
Outcomes	Wound sepsis, intraabdominal infections and extraabdominal infections within 30 days of surgery
Notes	NOS very high risk of bias overall
Risk of bias
Bias	Authors' judgement	Support for judgement
Representativeness of the exposed cohort	Low risk	CD patients who underwent surgical resection, stricturoplastly or intestinal bypass from 1998 to 2001
Selection of the non exposed cohort	Low risk	Both groups obtained from the same hospital and time period
Ascertainment of exposure	Low risk	Medical records were examined
Demonstration that outcome of interest was not present at start of study	Unclear risk	Information not provided
Comparability of cohorts (Controlled for critical factor/other medications)	High risk	Univariate analysis only
Comparability of cohorts (Controlled for additional factor)	High risk	Univariate analysis only
Assessment of outcome	Low risk	Medical records were examined
Was follow‐up long enough for outcomes to occur	Low risk	30 days
Adequacy of follow up of cohorts	Unclear risk	Information not provided