We aimed to evaluate the reliability and validity of the Ulcerative Colitis (UC) Endoscopic Index of Severity (UCEIS) and Mayo Endoscopy Score (MES) and to validate the Robarts Histopathology Index (RHI) and Nancy Index (NI) in pediatric UC. We examined rectosigmoid and pancolonic versions of each instrument.
Single-center cross-sectional study of 60 prospectively enrolled participants. Through central endoscopy review, 4 pediatric gastroenterologists assigned rectosigmoid and pancolonic (mean of 5 colonic segments) UCEIS and MES scores. Two blinded pathologists assigned rectosigmoid and pancolonic RHI and NI scores. We assessed reliability with intraclass correlation coefficients and weighted kappa statistics and explored construct validity with correlations, boxplots, and receiver operator characteristic curves.
The UCEIS and MES displayed almost perfect intra-rater and inter-rater reliability (intraclass correlation coefficient and weighted kappa ≥0.85), moderate-to-strong correlation with histologic/clinical activity and fecal calprotectin (FC), and very strong correlation with global endoscopic severity (r > 0.9). Rectosigmoid UCEIS and MES scores of 0 were highly specific (≥95%) for endoscopic and histologic remission throughout the colon. Pancolonic endoscopy scores correlated more strongly with histologic activity, clinical activity, and systemic inflammatory markers and better discriminated between degrees of active disease. RHI and NI showed moderate-to-strong correlation (r = 0.5–0.83) with endoscopic/clinical activity and FC.
Our findings support the reliability and construct validity of the UCEIS and MES and the construct validity of the RHI and NI in pediatric UC. Normal rectosigmoid findings predicted pancolonic healing, but, given active disease, pancolonic endoscopic assessment more accurately captured global disease burden.