P0289 Correlation between endoscopic scores and Nancy histological Index in ulcerative colitis: A real-world, single-center prospective study

Abstract Background The Nancy Histological Index (NI) and Ulcerative Colitis Endoscopic Index of Severity (UCEIS) are established tools for evaluating disease activity in ulcerative colitis (UC). This study aims to evaluate the correlation between UCEIS and NI scores in various clinical scenarios, including endoscopies performed during clinical flares (Group A), to assess mucosal healing post-treatment (Group B), at initial disease diagnosis (Group C) and during surveillance (Group D). Methods This prospective single-center study was conducted between June 2022 and October 2024, involving 179 patients with confirmed UC, as part of a pilot phase of implementing NI in our Histology Lab. Patients underwent colonoscopy or flexible sigmoidoscopy during which UCEIS and Mayo Endoscopic Score (MES) were independently assessed by two experienced endoscopists in the most affected colon segment. Biopsies from the same segment were scored for histological activity using the NI by two blinded to the endoscopic score pathologists. Statistical analyses were performed with SPSS version 29.0.1.1. Correlations between UCEIS/MES and NI scores were analyzed using Spearman’s correlation coefficient. The correlation coefficients between UCEIS/NI and MES/NI for each group were compared using the Z-test. All test were two-tailed, with p-values less than 0.05 considered statistically significant. Results Data from 179 patients (median age:54 years) were collected. Flares accounted for 62% of endoscopy indications, followed by surveillance (26.3%), mucosal healing (8.9%) and diagnosis (2.8%). Correlation coefficient between UCEIS (0-8) and NI (0-4) for all UC patients was rs=0.77 (95%CI:0.70-0.82; p<0.001), while correlation coefficient between MES (0-4) and NI was rs=0.71 (95%CI:0.63-0.78; p<0.001). Across different clinical settings, the correlation coefficients between UCEIS and NI were as follows: Group A: rs=0.54 (95% CI:0.39-0.66; p<0.001), group B: rs=0,84 (95%CI:0.58-0.94; p<0.001), group C: rs=0.75 (95%CI:-0.42-0.98; p=0.14) and group D: rs=0.74 (95%CI:0.57-0.85; p<0.001). The corresponding correlation coefficients between MES and NI were: Group A: rs=0.45 (95%CI:0.28-0.59; p<0.001), Group B: rs=0,80 (95%CI:0,49-0.93; p<0.001), Group C: rs=0.18 (95%CI:-0.84-0.98; p=0.76) and Group D: rs=0.72 (95%CI:0.54-0.84; p<0.001). The correlation coefficients between UCEIS/NI and MES/NI showed no significant differences across any group. Conclusion This study highlights a strong correlation between UCEIS or MES and NI scores across various clinical settings, reinforcing their complementary role in evaluating UC severity. These findings support the integration of histological and endoscopic indices for more comprehensive disease activity assessment.