P320 Accuracy of Faecal Calprotectin Level to Select Patients with Inflammatory Bowel Disease for a Chromoendoscopy Surveillance Programme

Nowadays chromoendoscopy is considered the gold standard to detect colonic displasia in patients with inflammatory bowel diseases (IBD). Active inflammatory endoscopical lesions impair displasia detection at chromoendoscopy, leading to repeat this exploration after healing the inflammatory lesions and increasing the cost of these endoscopic surveillance programs. Fecal calprotectin values have claimed to accurately identify patients without endoscopical lesions as appropriate candidates for performing a chromoendoscopy but cut-off values have not been standardised yet. Consecutive IBD patients scheduled for a surveillance chromoendoscopy with clinically non-active IBD (partial Mayo score = 0 for ulcerative colitis and Harvey–Bradshaw <4 for pancolonic Crohn’s disease) were asked to collect a stool sample 12–24 h before the start of bowel cleansing (that is, 1 or 2 days before chromoendoscopy) and keep it at −4ºC temperature into their fridge. Fecal calprotectin was analysed using a quantitative immunoassay high-range Quantum Blue the same day of chromoendoscopy. A C-reactive protein blood test was done too. A complete colonic chromoendoscopy with indigocarmin 0.2% was performed by a blinded endoscopist to calprotectin and C-reactive protein values. Receiver operator characteristics statistics were used to determine the optimal cut-off values for endoscopic inflammatory lesions. Forty chromoendoscopies were performed in 23 men (51.5%) and 17 women, mean age 51(12) years. Thirty-five patients had ulcerative colitis (84.8%) and five pancolonic Crohn’s disease. Complete endoscopic mucosa remission was observed in 31 (77.5%) with mild or moderate inflammatory mucosal lesions in 9 patients. Mean calprotectin level for patients with and without endoscopic lesions were 945.6 (152)and 540.4 (82.4) μg/g, respectively (p = 0.03). C-reactive protein blood values did not show any differences between both groups. Intraepithelial polymorphonuclear cells in colonic biopsies were found in 18 patients (45.5%) but with no association with higher levels of fecal calprotectin. A cut-off value of 450 μg/g could identify patients with endoscopic colonic inflammatory lesions with 100% sensitivity, 52% specificity, 40% positive predictive value, 100% negative predictive value, and an area under the ROC curve of 0.76, 95% CI (0.6–0.9), p = 0.03. In this study, a fecal calprotectin cut-off 450 μg/g could identify with high-specificity IBD patients as non-appropriate candidates for surveillance chromoendoscopy. However, optimal cut-off values must be reproduced and laboratory techniques should be standardised.