LAUSR

BACKGROUND The TUMMY-UC is a Patient Reported Outcome (PRO) measure for pediatric ulcerative colitis (UC) with an observer RO (obsRO) version for children <8 years. It includes eight items selected by concept elicitation interviews. We aimed to finalize the TUMMY-UC by cognitive interviews (stage-2) and to evaluate the index for its psychometric properties (stage-3). METHODS The TUMMY-UC items were first finalized during 129 cognitive debriefing interviews. Then, in a prospective-multicenter validation study, 84 children who either underwent colonoscopy or provided stool for calprotectin completed the TUMMY-UC and various measures of disease activity. Assessments were repeated after 7 and 21 days for evaluating reliability and responsiveness. RESULTS During stage-2, the items were formatted with identical structure to ensure conceptual equivalence, and weighted based on ranking of importance. In stage-3, the TUMMY-UC total score had excellent reliability in repeated assessments (intraclass correlation coefficient [ICC], 0.90 [95%CI 0.84-0.94]). It also had moderate to strong correlations with all constructs of disease activity: r=0.70 with UC endoscopic index of severity, r=0.63 with IMPACT questionnaire, r=0.43 with calprotectin, r=0.80 with the PUCAI, r=0.75 with global assessment of disease activity and r=0.46 with C-reactive protein (all p<0.015). The index had excellent discrimination of disease activity with a score<9 defining remission (AUROC=0.95 (95%CI 0.93-0.99)). The ΔTUMMY-UC showed high responsiveness and differentiated well between children who experienced changed from those with no change. CONCLUSIONS The TUMMY-UC, constructed from PRO and ObsRO versions, is a reliable, valid and responsive index, which can be now used in practice and clinical trials.