Validation of Rapid Fecal Calprotectin Assay “fCAL turbo” for Inflammatory Bowel Disease – Retrospective Comparative Study with Endoscopic Activity

Abstract Fecal calprotectin (FC) is a promising biomarker for diagnosis and treatment of inflammatory bowel disease, ulcerative colitis (UC), and Crohn’s disease (CD). An enzyme immunoassay (EIA) is widely used for FC detection, though the considerable lag time, up to several days, causes clinical management delay. This study was performed to examine the new rapid kit fCAL-turbo, which is based on a particle-enhanced turbidimetric immunoassay (15 minutes), by comparing FC values with other EIA assays (EliA, PhiCal, Bühlmann) and endoscopic scores. Using 94 samples, fCAL-turbo showed strong significant positive correlations with the other kits (Spearman’s r = 0.9178 − 0.9886). Of 74 UC patients, 69 underwent an endoscopy and fCAL-turbo reflected endoscopic activity with a moderate correlation with Mayo endoscopic subscore (MES) (r = 0.6945, others r = 0.6682 − 0.7013). Receiver operating characteristic analyses based on MES 0 vs. 1 − 3 showed a similar efficacy as compared to the other kits (cut-off and area under the curve: 89.70 µg/g and 0.8592, respectively, others 62.35 − 138.4 µg/g and 0.8280 − 0.8611, respectively). All 20 CD patients underwent endoscopy examinations and fCAL-turbo results had a moderate correlation with modified simple endoscopic score for CD (r = 0.5471, others r = 0.3049 − 0.6731). fCAL-turbo showed strong correlations with the other kits and also demonstrated excellent performance for predicting endoscopic remission of UC.