Patterns and Utility of Calprotectin in Patients with Microscopic Colitis

Calprotectin is a cytoplasmic-protein that is released upon neutrophilic activation. Measuring fecal-calprotectin (FC) is used for monitoring inflammatory bowel disease activity and distinguishing it from irritable bowel syndrome. However, its utility in other types of colitis has not been well-investigated. Cases of collagenous-colitis (CC) and lymphocytic-colitis (LC) between 2015 and 2020 were retrieved from our institution surgical pathology database. Endoscopy and histopathologic examination findings were reviewed to confirm the diagnosis. 15 CC and 13 LC cases were included as FC was done at the time of initial diagnosis (before therapy). 62 cases of normal endoscopy and histopathologic examination were selected as a control group. One-way analysis of the variance (ANOVA) and receiver operating curve (ROC) analysis of FC were performed. Abnormally elevated FC (> 50 ug/g) was identified in 77% and 64% of CC and LC cases, respectively. Only 1.6% of control cases had mildly elevated FC of 54 ug/g. The mean FC of CC and LC groups (246 and 214, respectively) were significantly higher than the control group (22.4); p= <0.05. LC and CC groups had no statistically significant difference in the mean FC (p = 0.8). The area under the curve was 0.93 with ROC analysis. At the suggested cut-off of 50 ug/g, the sensitivity was 78.6%, specificity was 98.4% with a likelihood ratio of 48.7. Fecal calprotectin can be elevated in patients with lymphocytic or collagenous colitis, however with no statistically significant difference between the two types. Therefore, it has the potential to be used as a marker for screening, diagnosis, and monitoring response to therapy in patients with microscopic colitis.