Nancy Histological Index and endoscopic activity, clinical activity, and disease extent in pediatric ulcerative colitis

OBJECTIVES: Data on relationships among disease assessment domains in pediatric ulcerative colitis (UC) remain limited. This study evaluated associations between histopathologic activity assessed by the Nancy Index (NI), endoscopic activity assessed by the Mayo Endoscopic Subscore (MES), clinical activity assessed by the Partial Mayo Score (PMS), and Montréal-classified disease extent in children with UC. METHODS: This retrospective cross-sectional study included UC patients aged 1-16 years who underwent colonoscopy with biopsy and had paired data from the same disease assessment episode. Associations were examined using multivariable logistic regression models. RESULTS: In age- and sex-adjusted models, increasing NI grades showed a significant dose-response association with MES: NI = 2 (odds ratio [OR]: 26.67, 95% confidence interval [CI] [1.83; 388.15]; p = 0.016), NI = 3 (OR: 83.29, 95% CI [5.37; 1290.84]; p = 0.002), and NI = 4 (OR: 191.71, 95% CI [11.34; 3241.88]; p < 0.001). Higher NI grades also showed a graded association with PMS, particularly NI = 3 (OR: 31.84, 95% CI [2.78; 365.12]; p = 0.005) and NI = 4 (OR: 53.56, 95% CI [4.77; 600.81]; p = 0.001). Each one-grade increase in NI was significantly associated with greater disease extent (OR: 1.55, 95% CI: [1.10; 2.18]; p = 0.012). CONCLUSION: Increasing histopathologic activity of UC in pediatric patients showed a strong dose-response association for endoscopic activity and, to a lesser extent, with clinical activity and disease extent. These findings suggest that histopathologic activity reflects multiple disease domains in pediatric UC and may have predictive value.