Ayoub 2018.

Study characteristics
Methods	Retrospective cohort. Study period: 2014 to 2016.
Participants	Country: USA. CD and UC patients who underwent major abdominal surgery. Patients actively treated with steroids were excluded
Interventions	1. Vedolizumab (n= 16) within 8 weeks of surgery 2. Biologics other than vedolizumab (n= 37) within 8 weeks of surgery 3. No preoperative biologic therapy (n=18)
Outcomes	Surgical site infection within 30 days of surgery
Notes	This study is an abstract. NOS very high risk of bias overall
Risk of bias
Bias	Authors' judgement	Support for judgement
Representativeness of the exposed cohort	Low risk	All patients who underwent major abdominal procedures due to IBD were screened
Selection of the non exposed cohort	Low risk	Both groups obtained from the same hospital and time period
Ascertainment of exposure	Unclear risk	No information provided
Demonstration that outcome of interest was not present at start of study	Unclear risk	No information provided
Comparability of cohorts (Controlled for critical factor/other medications)	Low risk	Excluded patients actively treated with steroids
Comparability of cohorts (Controlled for additional factor)	High risk	Did not control for any other variables
Assessment of outcome	Unclear risk	No information provided
Was follow‐up long enough for outcomes to occur	Low risk	30 days
Adequacy of follow up of cohorts	Unclear risk	No information provided