Uchino 2015.

Study characteristics
Methods	Retrospective cohort. Study period: 2012 to 2014
Participants	Country: Japan. UC patients who underwent IPAA. Patients who underwent with total colectomy without IPAA were ex c luded
Interventions	1. Preoperative biologic (n=44) within 12 weeks of surgery 2. Preoperative immunomodulator (n= 105) 3. Preoperative steroids (n= 113)
Outcomes	Surgical site infection within 30 days of surgery
Notes	NOS very high risk of bias overall Adjusted OR preoperative steroids, immunomodulators, and biologics were obtained from multivariate regression analysis.
Risk of bias
Bias	Authors' judgement	Support for judgement
Representativeness of the exposed cohort	Low risk	UC patients who underwent IPAA from 2012 to 2014
Selection of the non exposed cohort	Low risk	Both groups obtained from the same hospital and time period
Ascertainment of exposure	Low risk	Data was obtained from a prospectively maintained database
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
Comparability of cohorts (Controlled for additional factor)	High risk	Univariate analysis
Assessment of outcome	Low risk	Data was obtained from a prospectively maintained database
Was follow‐up long enough for outcomes to occur	Low risk	30 days
Adequacy of follow up of cohorts	Unclear risk	Information not provided