High Correlation Between Fecal Immunochemical Test and Fecal Calprotectin in the Evaluation of Activity in Patients with Inflammatory Bowel Disease

Background: The Fecal Immunochemical Test (FIT) is a wide available fecal biomarker that could evaluate the disease activity in IBD. The aim is to assess the correlation between the FIT and fecal calprotectin (FC) for evaluating IBD activity. Methods: Unicentric, transversal cohort study. Consecutive patients with IBD were included and FIT and FC were determined. The clinical activity was assessed with Truelove-Witts and Yamamoto-Furusho index for UC patients while Harvey-Bradshaw and CDAI for CD patients. Spearman’s rank correlation test was used to assess the correlation between FIT and FC. Sensitivity, specificity, and positive and negative predictive values for FIT and FC were calculated. Receiver operator curves were constructed. Results: A total of 206 patients were included. One hundred forty-eight (72%) patients had diagnosis of UC and 58 (28%) with CD. The median of FIT was 2.8 g/g (range, 2.6 – 2394 g/g) and the median for FC level was 265.5 g/g (range, 22 – 6285 g/g). There was a very good correlation between FIT with and FC in UC patients (rs= 0.745, P < 0.01) and moderate in CD patients (rs = 0.574, P < 0.01). A FIT cutoff of 2.6 g/g identified endoscopic activity in UC patients with a sensitivity of 78%, specificity of 86%, PPV of 91% and NPV of 67% with an AUC of 0.852 (95% IC 0.758-0.946). Conclusion: FIT can be an alternative fecal biomarker to assess the disease activity in UC patients.