P479 Reliability and responsiveness of histologic disease activity indices in Crohn’s Disease

Abstract Background The operating properties of histologic indices are poorly characterized in Crohn’s disease (CD) and no validated index exists. We assessed the reliability responsiveness indices/items, developed an exploratory index, compared different methods scoring. Methods Using baseline week 12 image sets from EXTEND placebo-controlled trial, blinded central readers scored 4 (the Global Histologic Activity Score [GHAS], Geboes [GS], Robarts Histopathology Index [RHI], Nancy [NHI]) 3 additional novel items identified by expert panel (mucin depletion, basal plasmacytosis, pyloric gland metaplasia ileum). Reliability were evaluated for a global score (4 colonic segments + ileum), segments) ileal (ileum only) using intraclass correlation coefficient (ICC) area under receiver curve (AUC), respectively. Change was defined treatment assignment improvement activity as measured on 100-mm visual analogue scale (VAS) testing. Exploratory backward stepwise linear regression analysis. Candidate independent variables with ICC ≥0.4 AUC ≥0.56. VAS served dependent variable. Results Paired images analysed 55 subjects. Inter-rater substantial to almost perfect (ICC=0.73-0.85) small large (treatment AUC=0.50-0.65; AUC=0.71-0.94). GHAS, GS, RHI, NHI reached minimum threshold (ICC ≥0.4) (AUC ≥0.56) regardless whether scores calculated worst affected segment, average included segments, or sum (Table 1-3). Five tested candidate predictors. Three developed, each consisting items: (neutrophils lamina propria, neutrophils epithelium, erosion/ulceration), (chronic inflammatory infiltrate, erosion/ulceration) erosion/ulceration). highly correlated NHI, coefficients ≥0.80 4). Conclusion existing similarly reliable responsive measuring CD activity, method calculating could be used clinical trials. Attempts at development did not offer benefit over current indices.