P0419Clinical Evaluation and method comparison of four fecal calprotectin assays

Background Fecal calprotectin (fCAL) is a reliable biomarker of intestinal inflammation, correlating strongly with endoscopic and histological findings. It is widely used to differentiate inflammatory bowel disease (IBD) from irritable bowel syndrome (IBS) and to monitor IBD disease activity, as recommended by most guidelines. Various assay technologies exist, including ELISA, particle-enhanced turbidimetric immunoassays (PETIA), and lateral flow immunoassays (LFIA). Due to the lack of international standardization, manufacturers apply their own calibration procedures. This study compared fCAL results from three assays by one manufacturer and one assay from another manufacturer using identical clinical samples. Methods A total of 416 subjects were included: symptomatic patients suspected of IBD or IBS, confirmed IBD cases (N = 127), IBS by Rome III criteria (N = 103), other GI disorders (N = 65), and healthy donors (N = 121). Pediatric participants included ages 4–10 (n = 8) and 11–21 (n = 48). Samples were stored at –20 °C, extracted manually for ELISA or with CALEX® Cap for PETIA and LFIA, and analyzed using BÜHLMANN fCAL® ELISA, fCAL® turbo (on ROCHE cobas® c501), Quantum Blue® fCAL extended (QB fCAL), and QUANTA Lite® Calprotectin Extended Range according to the manufacturer’s instructions (QLER, Werfen). Results ROC curves showed excellent discrimination between IBS and IBD (AUC 0.933 for fCAL turbo; 0.912 for QB fCAL) with no significant differences. BÜHLMANN recommends cut-offs of 80/160 µg/g for IBS/IBD and 100/300 µg/g for monitoring; QLER uses 50/120 µg/g. International and national guidelines also mention 150 and 250 µg/g as recommended cut-offs for the assessment of diagnosed IBD patients. Sensitivity and NPV at the lowest cut-off exceeded 91% and 85% for BÜHLMANN (80 µg/g) and 86% and 87% for QLER (50 µg/g). Specificity and PPV at the highest cut-off were >91% and 92% for BÜHLMANN (300 µg/g) and >95% and 98% for QLER (120 µg/g). Among 127 confirmed IBD patients, 17 showed discrepant results between manufacturers; 16 had active disease with fCAL turbo ≥80 µg/g but QLER <120 µg/g, and one was in remission with fCAL turbo >80 µg/g but QLER <50 µg/g. Conclusion The results presented here show that the BUHLMANN assays show high comparability and excellent performance for fecal calprotectin with close clinical alignment. The comparison between different manufacturers underlines the importance of a thorough clinical validation that includes endoscopic and histological assessment and the need for manufacturer specific cut-off levels including a grey zone for both IBS/IBD differentiation and diagnosed IBD patients allowing clinicians to risk-stratify their patients. Reference: 1. Berinstein, J.A. et al., 2019, The Clinical Accuracy of the BÜHLMANN fCAL ELISA in the Differentiation of Inflammatory Bowel Disease From Irritable Bowel Syndrome: A Multicenter Prospective Case-Control Study, Crohn’s & Colitis Conflict of interest: Dr. Reinhard, Christian: Employee of BÜHLMANN Laboratories AG Ueberschlag, Marie-Eve: Employee of BÜHLMANN Laboratories AG Niederberger, Christian: Employee of BÜHLMANN Laboratories AG Anchling, Leslie: Employee of BÜHLMANN Laboratories AG Kupchak, Petro: Employee of BÜHLMANN Laboratories AG Schuster, Thomas: Employee of BÜHLMANN Laboratories AG