Evaluation of mucosal healing in ulcerative colitis by fecal calprotectin versus fecal immunochemical test Short Title: Fecal calprotectin vs. FIT for mucosal healing

OBJECTIVES: We previously showed that a quantitative fecal immunochemical test (FIT) can predict mucosal healing (MH) in ulcerative colitis (UC). Fecal calprotectin (Fcal) has also been reported as an important biomarker of UC activity. The aim of this study was to compare the predictive ability of these two fecal markers for MH in UC. METHODS: FIT and Fcal were examined in stool samples from consecutive UC patients who underwent colonoscopy. Mucosal status was assessed via the Mayo endoscopic subscore (MES). RESULTS: In total, 105 colonoscopies in 92 UC patients were evaluated in conjunction with the FIT and Fcal results. Both FIT and Fcal results were significantly correlated with MES (Spearman rank correlation coefficient: 0.61 and 0.58, respectively). The sensitivity and specificity of the FIT values (< 100 ng/mL) for predicting MH (MES 0 alone) were 0.95 and 0.62, respectively, while those of Fcal (< 250 g/g) were 0.82 and 0.62, respectively. The sensitivities became similar when MH was defined as MES 0 or 1 (0.86 vs. 0.86). Although the predictability of MH evaluated by the area under the receiver operating characteristics curve was similar for the two fecal markers (FIT 0.83 vs. Fcal 0.82 for MES 0 alone), the FIT results were relatively robust regardless of the cutoff value selected. CONCLUSIONS: Both FIT and Fcal can efficiently predict MH in UC, but FIT appears to be more sensitive than Fcal for predicting MES 0 alone.