P437 Feasibility study of a Point-of-Care assay for rapid determination of anti-TNFα biologics in capillary blood

Abstract

Abstract Background Inflammatory bowel disease (IBD) patients benefit from therapeutic drug monitoring and personalized adjustment of anti-TNFα drugs such as adalimumab (ADL) and infliximab (IFX). Commercially available rapid assays allow the fast and easy measurement of ADL and IFX. Unfortunately, most ADL and IFX in-vitro diagnostic assays rely on serum as analyte matrix. This is a critical hurdle in point-of-care (POC) analysis, as it requires laboratory professionals, additional laboratory instruments and is time consuming. Therefore, two recently developed rapid tests for the determination of ADL and IFX that only require capillary blood (CB) or EDTA whole blood (WB) without further treatment are tested in a POC setup at three different study sites. The primary aim of this study is to demonstrate matrix equivalency of CB and EDTA WB compared to serum as reference. Methods This observational study was performed at three sites. Two sites in Switzerland, Clarunis Basel and Kantonsspital Baselland, and one site in France, Centre Hospitalier Universitaire de Saint-Étienne. Sample analysis was performed by healthcare professionals at the study sites with the established Quantum Blue® serum rapid tests and the newly developed capillary blood applications. Blood samples from patients under infliximab therapy were collected directly before infusion (trough level of drug). Samples from adalimumab-treated patients were collected irrespective of the injection schedule. In total, up to 100 IBD patients are anticipated in the study, 50 under infliximab therapy and 50 treated with adalimumab. This work evaluated the interim outcome after the analysis of 29 ADL and 18 IFX patients. Results Bland-Altmann analysis revealed a good agreement of CB and EDTA WB compared to serum for both IFX and ADL sample sets. The mean bias for the biologic’s trough level analysed in CB and compared to serum was 5.2% for IFX and -11.7% for ADL. Passing-Bablok analysis for CB versus serum resulted in a slope of 0.92 and an intercept at 0.08 for IFX and a slope of 0.86 and an intercept at -0.063 for ADL. A comparison of EDTA WB compared to serum revealed a mean bias of 7.8% for IFX and 7.4% for ADL. Passing-Bablok analysis for EDTA WB versus serum resulted in a slope of 1.00 and an intercept at 0.00 for IFX and a slope of 1.00 and an intercept at 0.30 for ADL. Conclusion The newly developed rapid Quantum Blue® assays for the determination of infliximab and adalimumab in capillary blood and EDTA whole blood are very well comparable to the analysis of either biologic in serum. This study furthermore demonstrated the assays are well suited to be used in a POC setting, such as infusion centres, rather than in a laboratory. Both assays are standardized to WHO reference material.