P0410Histologic Remission Assessment in Ulcerative Colitis Using Endocytoscopy

Abstract Background Histologic remission has emerged as a key therapeutic target in ulcerative colitis (UC). Endocytoscopy (EC), a real-time ultra-magnification imaging technique, may enable the evaluation of histologic healing without the need for biopsies. Our objective was to analyze the agreement between endocytoscopic assessment (ELECT index) and the histologic gold standard (Nancy index). Methods We included consecutive patients with UC undergoing surveillance colonoscopy. Endocytoscopy was performed during the procedure to evaluate the mucosa, focusing on the segment with the highest previously documented inflammatory activity and using 1% methylene blue staining. Histologic activity was estimated endocytoscopically using the ELECT index. Findings were compared with histology (Nancy index) from biopsies obtained from the same areas.Endoscopic activity was also evaluated using the Mayo endoscopic subscore and UCEIS, and clinical (PRO2) and biochemical activity (fecal calprotectin and C-reactive protein) were recorded. Results Twenty-seven patients with ulcerative colitis were included. Median age was 54 years (IQR 36–68), and 63% were women. Baseline characteristics and UC features are summarized in Table 1. Only three patients had demonstrated mucosal healing in prior endoscopies.Clinically, 63% reported one daily bowel movement without bleeding. Median fecal calprotectin was 38.9 µg/g (IQR 18.7–91.6), CRP 1.5 mg/L (IQR 0.5–4.75), hemoglobin 14.6 g/dL (IQR 13.6–15.4), and albumin 4.5 g/dL (IQR 4.4–4.7).Most patients were in endoscopic remission, with 92.5% scoring Mayo 0 and 89% UCEIS 0. Histologic remission based on the Nancy index was achieved in 84% (Nancy 0), while 16% showed activity (Nancy 2 or 3). The ELECT index showed a score of 0 in 66.7% of patients, and scores between 1 and 3 in the remainder.Regarding agreement between both indices, among the 21 patients with Nancy 0, 15 were classified as ELECT 0 and four as ELECT 1; only two had higher scores (2 and 3). Among the four patients with histologic activity (Nancy 2 or 3), three showed elevated ELECT scores (2 and 3), and one was classified as ELECT 0.The ELECT index demonstrated a sensitivity of 84%, specificity of 99%, positive predictive value (PPV) of 84.2%, and negative predictive value (NPV) of 98.9% compared with the Nancy index as the reference standard. Conclusion Endocytoscopy enables accurate assessment of histologic remission in patients with ulcerative colitis. The ELECT index demonstrated high concordance with the Nancy index, with an excellent negative predictive value, reinforcing its utility as a non-invasive tool in clinical practice. Conflict of interest: Dr. Suarez Ferrer, Cristina Julia: No conflict of interest Martin Arranz, Eduardo: No conflict of interest Rueda Garcia, Jose Luis: No conflict of interest Sanchez Azofra, Maria: No conflict of interest Amiama Roig, Clara: No conflict of interest García Ramírez, Laura: No conflict of interest Poza Cordon, Joaquin: No conflict of interest Martin Arranz, Maria Dolores: No conflict of interest