Lightner 2018 A.

Study characteristics
Methods	Retrospective cohort. Study period: 2014 to 2016
Participants	Country: USA. CD patients who underwent elective major abdominal surgery.
Interventions	1. Preoperative vedolizumab (n= 100) within 12 weeks of surgery 2. Preoperative anti‐TNF therapy (n= 107) within 12 weeks of surgery 3. No preoperative biologic therapy (n= 105)
Outcomes	Surgical site infection, mucocutaneous separation, anastomotic leak, 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 elective major abdominal surgery from 2014 to 2016
Selection of the non exposed cohort	Low risk	Both groups obtained from the same hospital and time period
Ascertainment of exposure	Low risk	Electronic medical records reviewed
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)	High risk	Did not control for other medications
Comparability of cohorts (Controlled for additional factor)	High risk	Did not control for additional factors
Assessment of outcome	Low risk	Electronic medical records reviewed
Was follow‐up long enough for outcomes to occur	Low risk	30 days
Adequacy of follow up of cohorts	Low risk	Excluded patients with less than 30 days of follow up