Gu 2013.

Study characteristics
Methods	Retrospective cohort. Study period 2006 to 2010
Participants	Country: USA. UC or indeterminate colitis ptints who underwent total proctocolectomy or subtotal colectomy with end ileostomy. Patients who underwent surgery for toxic megacolon, massive hemorrhage, colonic perforation, dyplasia or malignancy were exlcuded
Interventions	1. Anti‐TNF medication (n= 167) within 12 weeks of surgery for infliximab and within 4 weeks of surgery for adalimumab/certolizumab 2. No preoperative anti‐TNF medication (n= 421)
Outcomes	Pelvic sepsis, wound infection, anastomotic leak within 30 days
Notes	NOS very high risk of bias overall
Risk of bias
Bias	Authors' judgement	Support for judgement
Representativeness of the exposed cohort	Low risk	UC or indeterminate colitis ptints who underwent total proctocolectomy or subtotal colectomy with end ileostomy
Selection of the non exposed cohort	Low risk	Both groups obtained from the same hospitals and time period
Ascertainment of exposure	Low risk	Information obtained from prospective database
Demonstration that outcome of interest was not present at start of study	Unclear risk	Did not provide information
Comparability of cohorts (Controlled for critical factor/other medications)	High risk	Did not control for other medications
Comparability of cohorts (Controlled for additional factor)	High risk	Did not control of other factors
Assessment of outcome	Low risk	Information obtained from prospective database
Was follow‐up long enough for outcomes to occur	Low risk	30 days
Adequacy of follow up of cohorts	Unclear risk	No information provided