Fecal calprotectin from ileostomy output in patients with Crohn's disease.

Background: Fecal calprotectin (FC) is a reliable biomarker widely used for assessing disease activity and postoperative monitoring in patients with Crohn's disease (CD); however, its efficacy in patients with an ileostomy is poorly understood. Our study evaluated whether FC from the ileostomy output can be used to predict postoperative small bowel inflammation in patients with CD.

Methods: Data from patients with CD and an ileostomy who had undergone FC measurement between January 1, 2015, and December 30, 2022, were analyzed retrospectively. Patients were enrolled in the study if they had undergone FC tests with concurrent imaging and/or endoscopic studies, facilitating comparison between FC tests and imaging and/or endoscopic examinations. FC measured with the point-of care (POC) test was denoted as FC-POCT, and that measured using the enzyme-linked immunosorbent assay (ELISA) was denoted as FC-ELISA.

Results: This study analyzed 101 patients and 224 FC test results. FC concentration differed significantly in patients with signs of small bowel inflammation on imaging and/or ileoscopy compared with those in remission (FC-POCT: median 191.0 µg/g; interquartile range [IQR], 94.6-499.0 µg/g vs. 29.9 µg/g; IQR, 29.9-50.0 µg/g; P < 0.001; FC-ELISA: median 252.5 µg/g; IQR, 118.5-911.0 µg/g vs. 16.8 µg/g, IQR, 8.2-33.0 µg/g; P < 0.001). The optimal cutoff value for FC-POCT and FC-ELISA to distinguish between small bowel inflammation and remission was 63.3 µg/g (area under the curve [AUC], 0.90; 95% confidence interval [CI], 0.88-0.97) and 40.1 µg/g (AUC, 0.89; 95% CI, 0.79-0.99), respectively. We also compared the diagnostic accuracy between the POC and ELISA testing methods and found no statistically significant difference (P = 0.692).

Conclusions: FC from the ileostomy output is a valuable biomarker with high sensitivity and specificity for monitoring small bowel inflammation in postoperative patients with CD and an ileostomy.