Significance of Conducting 2 Types of Fecal Tests in Patients With Ulcerative Colitis

BACKGROUND & AIMS: We compared the diagnostic accuracy of the fecal calprotectin (FCP) test vs the fecal immunochemical blood test (FIT) in determining the endoscopic severity and predicting outcomes of patients with ulcerative colitis (UC). METHODS: We performed a nationwide study of 879 patients with UC, enrolled at medical centers across Japan, from March 2015 to March 2017. We collected data on fecal biomarkers, endoscopic severities, and other clinical indices from Cohort 1 (n = 427) and assessed the diagnostic accuracy of FCP measurement and FIT results in determining clinical severity, based on Mayo score, and endoscopic remission, based on Mayo endoscopic sub-score (MES) or UC endoscopic index of severity. We also followed 452 patients in clinical remission from UC (Cohort 2) for 12 months and evaluated the associations of FCP levels and FIT results with clinical recurrence. RESULTS: The levels of FCP and FIT each correlated with the MES and UC endoscopic index of severity. There were no significant differences in the areas under the curve of FCP vs FIT in distinguishing patients with MES <= 1 from those with MES >= 2 (P = .394) or in distinguishing patients with MES = 0 from those with MES >= 1 (P = .178). Among 405 patients in clinical remission at baseline, 38 (9.4%) had UC recurrences within 3 months and 90 (22.2%) had recurrences within 12 months. FCP >= 146 mg/kg (hazard ratio [HR], 4.83; 95% confidence interval [CI], 2.80-8.33) and FIT >= 77 ng/mL (HR, 2.92; 95% CI, 1.76-4.83) were independently associated with clinical recurrence within 12 months. UC recurred within 12 months in 69% of patients with levels of FCP >= 146 mg/kg and FIT >= 77 ng/mL; this value was significantly higher than the rate of recurrence in patients with levels of FCP146 mg/kg and FIT <77 ng/mL (31.5%, P < .001) or patients with levels of FCP<146 mg/kg and FIT >= 77 ng/mL (30.0%, P < .001). CONCLUSION: In a nationwide study of patients with UC in Japan, we found that the level of FCP and FIT could each identify patients with endoscopic markers of disease severity (MES >= 2). The combination of FCP and FIT results can identify patients in remission who are at risk for disease recurrence.