Non-Invasive Biomarker Monitoring in UC on Biologics

Ulcerative colitis (UC) is a long-term inflammatory bowel condition. Many patients are treated with intravenous biologic drugs such as infliximab or vedolizumab. Measuring the level of these drugs in the blood helps doctors adjust treatment, but results can take one to two weeks to come back. Volatile organic compounds (VOCs) are gases released from stool and urine that reflect activity in the gut, including gut bacteria and inflammation. They can be measured quickly and without needles. This study will find out whether VOCs in stool and urine can tell apart patients with adequate drug levels from those with low drug levels. It will also look at whether VOCs can identify patients whose UC is in remission versus those whose disease is flaring, and how VOCs relate to blood inflammation markers, gut bacteria and DNA methylation (chemical tags on genes). Adults with UC already receiving maintenance intravenous infliximab or vedolizumab at University Hospitals Coventry and Warwickshire will be invited to take part. Participants will provide stool, urine and blood samples at four of their routine infusion appointments. No extra visits are needed and treatment is not changed by the study.

Inclusion Criteria: * Age 18 years or older * Confirmed diagnosis of ulcerative colitis (clinical, endoscopic and histological criteria per ECCO guidelines) * Established on maintenance intravenous infliximab or vedolizumab * Attending the day unit for routine maintenance intravenous infusion Exclusion Criteria: * Pregnancy or lactation * Antibiotic use within the preceding 4 weeks * Active malignancy * Concomitant cytotoxic chemotherapy