Real World Data on Vedolizumab Concentration and Outcomes in Inflammatory Bowel Disease (IBD) Patients Switching From Intravenous (IV) to Subcutaneous (SC) Vedolizumab in University Hospital Center Osijek

This is a non-interventional, prospective study of participants with IBD who switched from intravenous to subcutaneous vedolizumab in the real world setting. The study will enroll approximately 30 participants. The data will be collected at the Department of Gastroenterology and Hepatology of University Hospital Center Osijek. All the participants will be assigned to a single observational cohort. All procedures (e.g., blood draw for serum trough concentration of vedolizumab, stool collection for fecal calprotectin or colonoscopy) will be done for routine clinical care. Data will be collected at baseline and at 6-12 months after switch from intravenous to subcutaneous vedolizumab. At baseline, data on age, gender, body mass, diagnosis, time from diagnosis, prior and concomitant therapy for IBD, comorbidities, time from switch from vedolizumab IV to vedolizumab SC, and vedolizumab serum trough concentration during vedolizumab IV therapy, will be collected. At control visit, data on concomitant therapy, adverse events, hospitalization, surgery and vedolizumab serum trough concentration during vedolizumab SC therapy, will be collected. For evaluation of disease remission at baseline and at control visit, Harvey-Bradshaw index (HBI) for Crohn's disease and Partial Mayo score (PMS) for ulcerative colitis (HBI \<5 or PMS \<2); or value of fecal calprotectin (\<150 µ/g); or Simple Endoscopic Score for Crohn's disease (SES-CD) and Mayo endoscopic subscore (MES) for ulcerative colitis (SES-CD \<3 or MES \<2), will be used.