Fecal Immunochemical Test and Fecal Calprotectin Results Show Different Profiles in Disease Monitoring for Ulcerative Colitis

Background/Aims: Both fecal immunochemical test (FIT) and fecal calprotectin (Fcal) results are useful biomarkers for ulcerative colitis (UC). However, the situations in which each marker should be used are largely unknown. Methods: A total of 110 colonoscopy intervals of UC patients were assessed, and correlations between changes in colonoscopic findings and changes in the two aforementioned fecal markers were examined. Results: Among patients with mucosal healing (MH) and negative FIT or Fcal results at the initial colonoscopy, FIT and Fcal findings exhibited accuracies of 93% (38/41) and 79% (26/33), respectively, for predicting the results of the subsequent examination. Among the 24 patients who showed endoscopic activity at the precedent colonoscopy and MH at the subsequent examination, positive-to-negative conversion of FIT and Fcal findings at the subsequent examination was observed in 92% (12/13) and 62% (8/13) of patients, respectively. Among the 43 patients who showed endoscopic activity at both the precedent and subsequent examinations, Fcal findings reflected the change in endoscopic activity better than FIT results (r=0.59, p<0.0001 vs r=0.30, p=0.054). Conclusions: The FIT is useful for confirming MH and the occurrence of relapse. In contrast, Fcal is useful for monitoring the mucosal status of patients with active inflammation.