Enzyme immunoassay for the determination of von Willebrand Factor (VWF) function in human plasma. The Collagen Binding Assay (CBA) can be used to differentiate between von Willebrand Disorder (VWD) Type I and Type II when used in conjunction with the VWF antigen (VWF:Ag) assay.
VWF is an important blood clotting protein, involved in both assisting platelet adhesion and stabilization of clotting factor VIII. In von Willebrand Disease (VWD) there is typically a partial quantitative deficiency (classified as VWD Type 1) or a qualitative deficiency (classified as VWD Type 2). VWD Type 3 is rare and characterised by virtually complete deficiency of VWF. Higher molecular weight multimers of VWF serve to bind activated platelets through specific membrane glycoproteins to connective tissue fibres exposed at wound sites and thus promote blood clotting and wound sealing2. The incidence of VWD worldwide is estimated at 1% to 3% but may be more common as mild cases may remain undetected. The CBA is an ELISA procedure that quantitates the collagen binding capacity (VWF:CB) of VWF to collagen coated microtitre wells. Collagen binding of VWF is associated with the higher molecular weight (HMW) forms of VWF, believed to be functionally more important in haemostasis than lower molecular weight forms (LMW). Therefore CBA may correlate more closely with VWF function and bleeding problems than regular ELISAs for VWF which measures total (LMW + HMW) VWF.