Supplementary Material for: Impact of Diagnostic Delay on Disease Course in Pediatric Versus Adult-onset Patients with Ulcerative Colitis: Data from the Swiss IBD Cohort

Introduction: Given the lack of data we aimed to assess the impact of the length of diagnostic delay on natural history of ulcerative colitis in pediatric (diagnosed <18 years) and adult patients (diagnosed ≥18 years). Methods: Data from the Swiss Inflammatory Bowel Disease cohort study were analyzed. Diagnostic delay was defined as interval between the first appearance of UC-related symptoms until diagnosis. Logistic regression modeling evaluated the appearance of the following complications in the long term according to the length of diagnostic delay: colonic dysplasia, colorectal cancer, UC-related hospitalization, colectomy, and extra-intestinal manifestations (EIM). Results: A total of 184 pediatric and 846 adult patients were included. Median diagnostic delay was 4 [IQR 2-7.5] months for the pediatric-onset group and 3 [IQR 2-10] months for the adult-onset group (P=0.873). In both, pediatric and adult-onset groups, length of diagnostic delay at UC diagnosis was not associated with colectomy, UC-related hospitalization, colon dysplasia, and colorectal cancer. EIM were significantly more prevalent at UC diagnosis in the adult-onset group with long diagnostic delay compared to the adult-onset group with short diagnostic delay (p = 0.022). In the long term, length of diagnostic delay was associated in the adult onset group with colorectal dysplasia (p=0.023), EIMs (p<0.001) and more specifically arthritis/arthralgias (p<0.001) and ankylosing spondylitis/sacroiliitis (p<0.001). In the pediatric-onset UC group, length of diagnostic delay in the long term was associated with arthritis/arthralgias (p=0.017); however, it was not predictive for colectomy and UC-related hospitalization. Conclusions: As colorectal cancer and EIMs are associated with considerable morbidity and costs, every effort should be made to reduce diagnostic delay in UC patients.