Potential of Fecal Calprotectin as an Objective Marker to Discriminate Hospitalized Patients with Acute Severe Colitis from Outpatients with Less Severe Disease.

Background: Acute severe colitis (ASC) is conventionally diagnosed by Truelove and Witts' criteria which are non-specific and can be affected by other pathologic conditions. Fecal calprotectin (FCP) is a gut-specific marker of inflammation which can predict short-term outcomes in patients with ASC. We aimed to define the role of FCP in the diagnosis of ASC.

Methods: This prospective observational cohort study included adult patients (> 18 years) with ulcerative colitis (UC) for whom FCP was measured and was under follow-up from April 2015 to December 2016. Patients were divided into two cohorts: (1) all consecutive hospitalized patients with ASC as defined by Truelove and Witts' criteria; (2) outpatients with active UC (defined by Mayo score) who did not fulfill Truelove and Witts' criteria. FCP levels were compared between the two cohorts, and a cutoff for FCP to diagnose ASC was determined.

Results: Of 97 patients, 49 were diagnosed with ASC (mean age: 36.1 ± 11.9 years, 36 males) and 48 with active UC (mean age: 37.9 ± 12.4 years, 25 males). Median FCP levels were significantly higher in patients with ASC [1776(952-3123) vs 282(43-568) µg/g, p < 0.001] than mild to moderately active UC (n = 48) or moderately active UC [n = 35, 1776(952-3123) vs 332(106-700) µg/g, p < 0.001]. A FCP cutoff of 782 μg/g of stool had excellent diagnostic accuracy, with an area under the curve of 0.92(95% CI 0.87-0.97), sensitivity of 84% and specificity of 88% to differentiate ASC from active UC.

Conclusion: FCP could differentiate ASC from mild to moderate patients with UC, but requires validation before clinical use.