Development and Validation of the Mucosal Inflammation Noninvasive Index For Pediatric Crohn's Disease

BACKGROUND & AIMS: Mucosal healing (MH) has become a goal of therapy for Crohn's disease (CD), but frequent endoscopies are not feasible. We aimed to develop and validate a non-invasive index to assess mucosal inflammation in children with CD. METHODS: We collected data from the multi-center prospective ImageKids study, in which children with CD underwent ileocolonoscopy with magnetic resonance enterography. We investigated the association of pediatric CD activity index (PCDAI) items and laboratory test results with the simple endoscopic score for CD (SESCD). We used these data in a blended mathematical judgmental clinimetric approach to develop a weighted categorized index to identify children with CD who have MH, which we called the MINI index. We validated the index using data from 3 independent patient cohorts. The derivation and validation cohorts included 154 and 168 children, respectively (age 14.1 +/- 2.5 years and 14.2 +/- 3.9 years), of whom 16% and 36% had MH (defined as SESCD<3). RESULTS: In multivariable models, the stooling item of the PCDAI, erythrocyte sedimentation rate, and level of fecal calprotectin were associated with SESCD (all P < .05). We added data on level of C-reactive protein to develop the MINI index. MINI scores below 8 identified children with MH with 88% sensitivity and 85% specificity in the derivation cohort and with 84% sensitivity and 87% specificity in the validation cohorts. Ninety percent of the patients in the validation cohort with scores of 8 or more had active mucosal inflammation, yet 78% of patients with scores below 8 had MH. Scores below 6 increase the positive predictive value to 86%. CONCLUSIONS: We developed an index to non-invasively assess mucosal inflammation in children with CD. This index, identifies children with MH with high sensitivity and specificity. The added benefit of MINI over measurement of fecal calprotectin was small but significant, especially for patients with concentrations of fecal calprotectin from 100 to 599 mu g/g.