Yamada 2017.

Study characteristics
Methods	Retrospective cohort. Study period: 2014 to 2016
Participants	Country: USA. UC and CD patients who underwent major and minor abdominal surgeries. Patients with less than 30 days of follow up data or missing data were excluded
Interventions	1. Preoperative anti‐TNF therapy (n= 129) within 4 weeks of surgery 2. Preoperative vedolizumab (n= 64) within 4 weeks 3. No preoperative biologic therapy (n= 250)
Outcomes	Infectious complications (wound infection or dehiscence, anastomotic leak, abscess, sepsis, fistula, pulmonary infection, UTI) within 30 days of surgery
Notes	NOS very high risk of bias overall Adjusted OR for preoperative steroids was obtained from multivariate model.
Risk of bias
Bias	Authors' judgement	Support for judgement
Representativeness of the exposed cohort	Low risk	UC and CD patients who underwent major and minor abdominal surgeries from 2014 to 2016
Selection of the non exposed cohort	Low risk	Both groups obtained from the same database 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	Low risk	Patients with less than 30 days of follow up data or missing data were excluded