Clinical implications of fecal calprotectin and fecal immunochemical test on mucosal status in patients with ulcerative colitis

Although fecal calprotectin (Fcal) and the fecal immunochemical test (FIT) have been associated with endoscopic activity in ulcerative colitis (UC), the clinical implications of each marker depending on the mucosal status are not well known. A total of 174 results obtained from 128 patients with UC who simultaneously underwent colonoscopy and fecal tests were retrospectively evaluated from March 2015 to February 2018. The correlation and predictability of fecal markers as a surrogate marker of endoscopic activity, and the sensitivity, specificity, and predictive value of fecal tests for mucosal healing were statistically evaluated. Both fecal tests showed a statistically significant correlation with Mayo Endoscopic Subscore (MES) (Fcal: r = 0.678, P < .001 and FIT: r = 0.635, P < .001) and Ulcerative Colitis Endoscopic Index of Severity (UCEIS) (Fcal: r = 0.711, P < .001 and FIT: r = 0.657, P < .001). Fcal was statistically superior to FIT in predictive accuracy for endoscopic activity (area under the curve [AUC]: 0.863 vs 0.765 with MES, P < .001 and AUC; 0.847 vs 0.757 with UCEIS, P < .001). FIT was superior to Fcal in sensitivity for mucosal healing (98.0% vs 78.4% with MES, 94.9% vs 74.6% with UCEIS). Fcal and FIT were well correlated with endoscopic activity in UC and can be surrogate markers of mucosal inflammation. Depending on mucosal status, Fcal was more accurate in predicting the endoscopic activity in active inflammation, whereas FIT was more sensitive in predicting the achievement of mucosal healing.