P412 Faecal Calprotectin as a predictor of endoscopic and histologic remission in patients with Ulcerative Colitis

Abstract

Abstract Background Faecal calprotectin (FCP) is a reliable surrogate marker for disease activity in ulcerative colitis (UC). However, there are no consensus cut-off values for histoendoscopic remission. The aim of the study is to correlate FCP with Mayo Endoscopic Score (MES) and histological disease activity (Geboes score) of UC patients in clinical remission. Methods We performed a prospective study including adult UC patients at the McGill IBD Center between 2013 and 2017. Patients in clinical remission (partial Mayo score ≤2) or disease relapse, undergoing endoscopy for disease activity or dysplasia surveillance, were enrolled. Before bowel preparation, FCP was collected. MES was documented during colonoscopy. Biopsies were taken throughout the colon and histological activity was assessed using Geboes score (GS) by a blinded expert gastrointestinal pathologist. Results The study included 253 patients, of which 117 (46%) were male with a mean age of 38.2 years (standard deviation [SD] ± 24.8). 46% of the patients had pancolitis at the time of colonoscopy. 5-aminosalicylate were used by 68.4% of patients while 20.9% were on immunomodulators, 19% on biologics and 0.4% on small molecules as treatment. Regarding endoscopic correlation, it showed that an FCP ≥ 200 μg/g predicts MES > 1 despite clinical remission, yielding sensitivity of 59% and specificity of 74%. A FCP ≥ 123 predicts MES > 0 despite clinical remission (58% sensitivity and 70% specificity), also aiding to differentiate MES 0 from MES 1 (61% sensitivity and 70% specificity). As to histologic correlation, a FCP ≥ 80 μg/g identified histological disease activity using Geboes criteria (GS score > 3.1) in patients with clinical remission, yielding 64.7% sensitivity, 58.7% specificity and 77% positive predictive value (Figure 1). When using a GS score threshold of > 2, a cut-off value of FCP ≥ 50 μg/g, appears to be the most clinically relevant to identify patients in clinical remission who continue to have active histologic inflammation, with an 49.6% sensitivity, 41.6% specificity and 40% positive predict value. Results are summarized in Table 1. Conclusion FCP correlates very well with endoscopic and histologic disease activity and can be used as a surrogate marker for disease activity. Our study prospectively demonstrated the optimal cut-off values helping to discriminate endoscopic healing and histologic remission.