Liang 2017.

Study characteristics
Methods	Retrospective cohort. Study period: 2014 to 2016
Participants	Country: USA. UC and CD patients who underwent lower GI surgery
Interventions	1. Preoperative anti‐TNF therapy (n= 686) within 12 weeks of surgery 2. Preoperative vedolizumab (n= 114) 3. Preoperative ustekinumab (n= 8) 4. Preoperative 5ASA (n= 733) 5. Preoperative corticosteroids (n= 674) 6. Preoperative immunosuppressants (n= 382) 7. No preoperative anti‐TNF therapy (n= 2674) 8. No preoperativ vedolizumab (n= 3246) 9. No preoperative ustekinumab (n= 3352) 10. No preoperative 5ASA (n= 2627) 11. No preoperative corticosteroids (n= 2686) 12. No preoperative immunosuppressants (n= 2978)
Outcomes	Wound infection, peritonitis, retroperitoneal infection, sepsis within 30 days of surgery
Notes	NOS very high risk of bias overall Adjusted OR for preoperative corticosteroids was obtained from multivariate regression model.
Risk of bias
Bias	Authors' judgement	Support for judgement
Representativeness of the exposed cohort	Low risk	UC and CD patients who underwent lower GI surgery
Selection of the non exposed cohort	Low risk	Both groups obtained from Clinformatics DataMart database and time period
Ascertainment of exposure	Low risk	Identified exposures using medical and pharmacy claims
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	Univariate analysis
Comparability of cohorts (Controlled for additional factor)	High risk	Univariate analysis
Assessment of outcome	Low risk	Identified outcomes using ICD codes, facility claims and provider claims
Was follow‐up long enough for outcomes to occur	Low risk	30 days
Adequacy of follow up of cohorts	Unclear risk	Did not provide information