Development, validation, and evaluation of a pediatric ulcerative colitis activity index: a prospective multicenter study.

Colonoscopic appearance, the primary measure of disease activity in adult ulcerative colitis, is less acceptable to children. Our aim was to develop a noninvasive activity index of pediatric ulcerative colitis. Item selection was performed judgmentally using a Delphi group of 36 experts in pediatric inflammatory bowel disease. Item weighting was performed by regression modeling using a prospective cohort of 157 pediatric ulcerative colitis patients. Validation was assessed on a separate prospective cohort of 48 children with ulcerative colitis undergoing complete colonoscopy. Responsiveness was evaluated at a follow-up visit of 75 children using effect size statistics and diagnostic utility approaches. A list of 41 items was generated and reduced to 11 by rank order. Two physicians completed the Pediatric Ulcerative Colitis Activity Index (PUCAI) on each of the patients in the weighting cohort. Six clinical items were significant in the regression analysis; the laboratory items and an endoscopic appearance item did not improve the PUCAI performance. In the validation cohort, the PUCAI was highly correlated with the Physician's Global Assessment (r = 0.91, P < .001), Mayo score (r = 0.95, P < .001), and colonoscopic appearance (r = 0.77, P < .001). Correlations were higher than 2 noninvasive adult indices calculated concurrently. Interobserver and test-retest reliability were excellent (intraclass correlation coefficient = 0.95; 95% CI: 0.93-0.97). Cut-off points were established using receiver operator characteristic curves on the full cohort. Excellent responsiveness was found at repeated visits (effect size = 1.9, area under the receiver operator characteristic curve = 0.97). The rigorously developed PUCAI is a noninvasive, valid, highly reliable, and responsive index with which to assess disease activity in pediatric ulcerative colitis.