Noninvasive Fecal Immunochemical Testing and Fecal Calprotectin Predict Mucosal Healing in Inflammatory Bowel Disease: A Prospective Cohort Study

Background: The noninvasive biomarkers fecal immunochemical testing (FIT) and fecal calprotectin (FCP) are sensitive for prediction of mucosal inflammation in inflammatory bowel disease. However, neither test has yet been shown to independently and accurately predict mucosal healing (MH). We aimed to assess the specificity of noninvasive FIT and FCP for MH prediction. Methods: In this prospective cohort study of adult inflammatory bowel disease outpatients presenting for colonoscopy, stool samples for FIT and FCP were collected 48 hours before endoscopy. Using MH defined by Simple Endoscopic Score for Crohn's disease (SES-CD = 0), Rutgeert's score (i0), and the Ulcerative Colitis Endoscopic Index of Severity (UCEIS = 3), receiver operator characteristic curves were plotted, and sensitivity, specificity, positive and negative predictive values, and areas under the curve were calculated. Multivariate logistic regression analysis was used to develop a clinical model for noninvasively predicting MH. Results: Eighty patients (40 Crohn's disease and 40 ulcerative colitis) were enrolled. The specificities of FIT < 100 ng/mL and FCP < 250 mu g/g for MH were 0.57 (95% confidence interval, 0.38-0.74) and 0.77 (0.57-0.89), respectively. Positive predictive values for MH for FIT,100 ng/mL and FCP < 250 mu g/g were 0.78 (0.64-0.87) and 0.77 (0.58-0.90), respectively. In multivariate modeling, combining FIT, FCP, and clinical symptomatic remission improved specificity for MH to 0.90 (0.72-0.97) with positive predictive values of 0.84 (0.60-0.96). Areas under the curve for FIT was higher for patients with ulcerative colitis (0.88) than for patients with Crohn's disease (0.69, P = 0.05). Conclusions: FIT and FCP have similar performance characteristics for identifying MH. Combined, low FIT, low FCP, and clinical remission are specific for MH.