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Introduction: Non‐factor replacement therapies are emerging as prophylactic treatment options in haemophilia A or B (HA/HB) with and without inhibitors. Concizumab is an anti‐tissue factor pathway inhibitor (TFPI) monoclonal antibody preventing factor (F)Xa inhibition and enhancing thrombin generation. Based on experience with other non‐factor therapies and extended half‐life products, there is a focus on potential interference with common clinical coagulation assays used to monitor patients treated with concizumab. Aim: To evaluate the impact of concizumab on standard clinical coagulation assays. Methods: Plasma samples (normal, HA/HB with/without inhibitors) in the presence/absence of added concizumab (250–16,000 ng/mL) were analysed in clinical assays including activated partial thromboplastin time (aPTT), prothrombin time (PT), FVIII and FIX one‐stage clot and chromogenic substrate assay, assays for detecting FVIII or FIX inhibitors and other assays for coagulation factors. Results: Concizumab did not impact PT assays, but resulted in a small shortening of aPTT (up to 5 s in haemophilia plasma and 0.4 s in normal plasma). Concizumab had no, or only a minor impact on FVIII and FIX activity assays or Bethesda inhibitor assays. FXI and FXII activity in normal plasma, as measured by single factor aPTT‐based assay, was significantly increased in the presence of concizumab (+11% each). This was also the case for FVII and FX measured by PT‐based assays using plasma with 25% of FVII or FX (+64% and +22%, respectively). Conclusion: The presence of concizumab did not, or only slightly, influence the outcome of standard clinical coagulation assays relevant for HA and HB. [ABSTRACT FROM AUTHOR]

Introduction: The development of neutralising (inhibitors) and non‐neutralising antibodies (NNAs) is a complication to factor replacement therapy in haemophilia. The diagnostic methods available lack standardisation, have high inter‐laboratory variation, and false‐negative as well as false‐positive results may affect treatment. Both functional inhibitors and NNAs may be detected with higher reproducibility, sensitivity and specificity using the immunological Luminex xMAP‐based fluorescence‐immunoassay (xFLI). Aim: Validation of our xFLI and comparability with enzyme‐linked immunosorbent assay (ELISA) and chromogenic Nijmegen‐Bethesda assay (CBA) for anti‐FVIII antibodies in haemophilia A (HA) patients. Methods: The xFLI method was developed with full‐length and B‐domain deleted factor coupled to magnetic beads, optimised and validated for performance characteristics. Comparability with ELISA and CBA was evaluated in HA patient samples (n = 112), serial samples in six inhibitor patients and reference interval and decision‐limits in healthy donors (n = 44). Results: The intra‐ and inter‐assay precision (CV%) for the xFLI method was below 6% and detection limit (LLOQ).084 ng/mL (NovoEight). All ELISA‐positive samples were positive with either Advate or NovoEight. Additionally, 10.7%–14.3% were xFLI‐positive and ELISA‐negative. All but one CBA‐positive sample was above 3SD with xFLI; one was between 2 and 3SD. 29.1% were xFLI‐positive and CBA negative. The overall concordance between xFLI and ELISA was 82.1% and xFLI and CBA 77.9%. Conclusion: The anti‐FVIII antibody xFLI method is adaptable to clinical practice and more sensitive and reproducible than ELISA and CBA. Actual NNA titers are determined to both full‐length and B‐domain deleted FVIII. The xFLI is thus valuable for confirmation of all anti‐FVIII antibodies. [ABSTRACT FROM AUTHOR]

Nanoparticles (NPs) are increasinglyused in diagnostic and drugdelivery. After entering the bloodstream, a protein corona will formaround NPs. The size and curvature of NPs is one of the major characteristicsaffecting the composition of bound protein in the corona. Key initiatorsof the intrinsic pathway of blood coagulation, the contact activationcomplex, (Kallikrein, Factor XII, and high molecular weight Kininogen)have previously been identified on NPs surfaces. We show that thefunctional impact of carboxyl-modified polystyrene NPs on these initiatorsof the intrinsic pathway is size dependent. NPs with high curvatureaffect the enzymatic activity differently from NPs with low curvature.The size dependency is evident in full blood plasma as well as insolutions of single coagulation factors. NPs induce significant alterationof the enzymatic activity in a size-dependent manner, and enzyme kineticsstudies show a critical role for NPs surface area and curvature. [ABSTRACT FROM AUTHOR]