S0662 Evaluating the Optimum Number of Biopsies to Assess Histologic Inflammation in Ulcerative Colitis

INTRODUCTION: Histology is an emerging treatment target in ulcerative colitis (UC). We evaluated the minimum number of biopsies needed to accurately assess histologic activity in UC. METHODS: A convenience sample of UC patients with ≥4 rectosigmoid biopsies, and corresponding clinical and endoscopic data, was obtained from the University of California, San Diego biobank. Histology and endoscopic videos were evaluated by blinded central reading. A 4-biopsy Robarts Histopathology Index (RHI) reference score, consisting of the worst item-level ratings across the 4 biopsies, was compared to 1-, 2-, and 3-biopsy scores. Agreement was evaluated using bivariate errors-in-variable regression analysis (acceptance interval [AI]: ± 0.25 standard deviation of maximum reference score). Geboes (GS) and Visual Analog scale (VAS) estimates were similarly assessed. Subgroup analyses were performed according to endoscopic activity and disease location. RESULTS: A total of 46 patients had ≥ 4 rectosigmoid biopsies available. The 2-biopsy (tolerance interval [TI]: −7.66, 4.79) and 3-biopsy (TI: −4.86, 3.46) RHI scores agreed with the 4-biopsy score, whereas the 1-biopsy score did not (TI: −13.99, 7.78). Using 2-, 3-, and 4-biopsies yielded similar mean ± standard deviation RHI scores (6.1 ± 9.6, P = 0.36; 6.8 ± 10.5, P = 0.7; 7.5 ± 11.2, respectively) and identical histologic remission rates (65.2%, P = 1.0). Using 1 biopsy yielded numerically different mean RHI scores (4.4 ± 8.1, P = 0.06) and histologic remission rates (71.7%, P = 0.65). Similar findings existed for the VAS. For the GS, there was only agreement between the 3- and 4-biopsy scores (Table 1). For the RHI, agreement existed between 3- and 4-biopsies in both the endoscopically active and inactive subgroups whereas agreement between the 2- and 4-biopsies was observed in the endoscopically inactive, but not active, subgroup (Table 2). Scores based on rectosigmoid biopsies did not agree with those based on ascending or transverse colon biopsies (Table 3). Histologic remission rates were lower when biopsies from all three locations were used compared to the rectosigmoid alone (33.3% vs 61.9%, P = 0.1). CONCLUSION: A minimum of 2 biopsies accurately assesses UC disease activity in the rectosigmoid colon when using the RHI. Further studies of endoscopically active patients, and multiple sampling locations are needed. These findings have implications for biopsy sampling strategies both in clinical trials and routine practice.Table 1Table 2Table 3

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