The Utility of Fecal Calprotectin in the Diagnosis and Management of Microscopic Colitis.

Background: The incidence of microscopic colitis has increased over time. To date, there is no specific biomarker for microscopic colitis, and the diagnosis relies on histopathological tissue obtained during colonoscopy which is an invasive and costly procedure. Unlike Crohn's disease and ulcerative colitis, the utility of fecal calprotectin in diagnosing or monitoring microscopic colitis has not been established, and studies on the role of fecal calprotectin in microscopic colitis are limited. In this retrospective study, we analyzed the utility of this biomarker in the diagnosis of microscopic colitis. Methods: The medical records of patients who have been diagnosed with collagenous colitis and lymphocytic colitis aged 18-89 years old were retrospectively reviewed. Patient characteristics were recorded in those who had fecal calprotectin measured. Results: There were 198 patients who were diagnosed with collagenous colitis and lymphocytic between October 1, 2015, and July 31, 2022. Twenty-three patients had fecal calprotectin levels measured and were included in this study. The mean age was 51.7 ± 7.8 years in all groups. Thirteen patients were female. Six patients (26.1%) were diagnosed with collagenous colitis, and 17 patients (73.9%) were diagnosed with lymphocytic colitis. The fecal calprotectin cut-off in this lab is 50 μg/g stool. Median fecal calprotectin levels were 30.1 μg/g (15.6, 122.5), 19.5 μg/g (16.5, 64.6), and 33.2 μg/g (15.6, 134.9) in all groups, collagenous colitis, and lymphocytic colitis, respectively. Conclusion: The utility of fecal calprotectin in diagnosing microscopic colitis is limited. Our study suggests the diagnosis should be based on histopathology tissue obtained during colonoscopy.