Objective: Non-invasive stool tests, including the fecal immunochemical test (FIT) and fecal calprotectin (FC), are reliable biomarkers for mucosal healing (MH) in ulcerative colitis (UC). However, which fecal test is superior for predicting MH in inactive UC patients requires evaluation. We aimed to compare the accuracy of FIT and FC results for predicting MH in quiescent UC patients.Methods: This prospective, multicenter study was conducted at three tertiary hospitals. UC patients in clinical remission for at least three months underwent colonoscopy and MH was evaluated using the Mayo endoscopic sub-score (MES). The receiver operating characteristic (ROC) curve and cutoff value with the best accuracy for predicting MH were assessed.Results: Among 127 patients, 65 (51.2%) showed MH (MES = 0). The area under the curve (AUC) for predicting MH (MES = 0) was significantly higher for FC than for FIT (AUC 0.858 (95% confidence interval (CI) 0.784-0.913) vs. 0.707 (95% CI 0.620-0.784), p < .001); there was no difference when MH included MES = 1 (MES ≤ 1) (AUC 0.820 (95% CI 0.742-0.883) vs. 0.813 (95% CI 0.734-0.877), p = .891). When the cutoff value was 70 μg/g for FC and 10 ng/mL for FIT, the sensitivity, specificity, positive predictive value and negative predictive value were 89.2, 71, 76.3, and 86.3, respectively, for FC and 92.3, 50, 65.9, and 86.1, respectively, for FIT.Conclusion: FC is more accurate than FIT for predicting MH in quiescent UC patients. The superiority of FC might be related to the distinctive performance of FC in differentiating inflammatory levels, particularly in low-grade mucosal activity.
Keywords: Fecal calprotectin; fecal immunochemical test; remission; ulcerative colitis.