P473 Comparison of clinical performance of fecal calprotectin of laboratory methods with lateral flow based POC and home tests

Abstract Background To confirm an IBD diagnosis and manage IBD patients, endoscopy is the gold standard to assess mucosal inflammation. Fecal calprotectin (fCAL) is a reliable biomarker of intestinal inflammation that highly correlates with endoscopic and histological findings. Fecal calprotectin testing is recommended in most IBD guidelines for diagnosis and disease course evaluation. Different assay technologies exist that need to measure fecal calprotectin comparably. These range from classic enzyme linked immunosorbent assays (ELISA), particle enhance turbidimetric immuno assays (PETIA), and rapid lateral flow assays (LFIA). LFIA[AL1] [RC2] s can be read by conventional tabletop readers or by everyday smartphone applications using the phone’s camera to acquire an image, detect the test cassette and calculate a quantitative result. As there is no international standard to date, fecal calprotectin assay manufacturers rely on their own internal calprotectin standardization. This study compared four different assays measuring the same clinical samples. Methods The 128 raw stool samples that were analyzed in this study were obtained from patients that presented with signs and symptoms suggesting intestinal inflammation and underwent endoscopic evaluation to establish or exclude an IBD diagnosis. Samples were extracted with the BÜHLMANN CALEX® Cap stool extraction device. Each extract was then measured on the BÜHLMANN fCAL® ELISA, fCAL® turbo (PETIA), Quantum Blue® fCAL extended lateral flow assay and smartphone based IBDoc® fCAL home test. For the home test, two phones, iPhone 11 and Samsung Galaxy S7, were used to measure the lateral flow test cassettes. Each sample was measured one time on each assay and Receiver Operating Characteristic (ROC) curve analysis was performed and total agreement between each method was calculated. Results ROC curves were generated to assess the ability of each assay to differentiate between IBS and IBD with area under the curve (AUC) values ranging from 0.827 (Samsung Galaxy S7 to 0.835 (fCAL turbo). There was no significant difference between the methods. Commonly used cut-offs in the assessment of IBD patients are 100 and 250 µg/g, respectively. Positive and negative percent agreement (PPA/NPA) between the smartphone-based home test and the laboratory assays was calculated. The PPA was above 90% for all methods while the NPA was above 88% for all methods. Conclusion The results presented here show that the four BÜHLMANN assays measure fecal calprotectin extremely comparably and show an excellent clinical performance. This allows for the use of the methods interchangeably, depending on the needs of the patients and their care team.