Analytical and Clinical Validation of a Non-Ristocetin Based VWF Assay on 2 Automated Analyzers in a Large Reference Laboratory.

Background: Historically, von Willebrand factor (VWF) activity assays utilized ristocetin despite limitations including poor limits of detection and high imprecision. Newer VWF activity assays such as the INNOVANCE® VWF Ac assay, however, do not rely on ristocetin to measure platelet-dependent VWF function. The purpose of this study was to evaluate the analytical and clinical performance of the Siemens Healthineers INNOVANCE VWF Ac Assay on the Siemens BCS® XP and the Sysmex® CS-2500 systems in a large reference laboratory setting.

Partial glycosylation at asparagine-2181 of the second C-type domain of human factor V modulates assembly of the prothrombinase complex.

Thrombin-activated factor Va exists as two isoforms, factor Va(1) and factor Va(2), which differ in the size of their light chains and their affinity for biological membranes. The heterogeneity of the light chain remained following incubation of factor Va with N-glycanase. However, we found that the factor V C2 domain, which contains a single potential glycosylation site at Asn-2181, was partially glycosylated when expressed in COS cells.

Monocyte/macrophage regulation of coagulant events.

Monocytes/macrophages actively regulate both the assembly and function, as well as the substrate specificity, of various coagulation enzymes at their membrane surface. Regulation is effected through a variety of mechanisms, not limited to, but including the expression of receptors (or 'binding sites') for the various protein constituents of the complexes, the expression of different receptors which may alter the function of the protease, and the expression of membrane proteases which may affect protein cofactor function. Monocyte stimulation with various agonists modulates many of these responses as does their adherence to and differentiation on various substrates.