Assays used for diagnosing von Willebrand disease (VWD)

Assay name	What it measures	Method
VWF activity
VWF activity: Platelet binding	Ability of VWF to bind to:	Quantitate binding of plasma VWF to:
VWF:RCo (ristocetin cofactor activity)	Fixed normal platelets in the presence of ristocetin	Platelets; assess agglutination using dilutions of plasma to quantitate VWF
VWF:GPIbR (binding to platelet glycoprotein Ib)	Recombinant GPIb in the presence of ristocetin	Recombinant GPIb using an ELISA plate or latex or magnetic beads
VWF:GPIbM (binding to a platelet glycoprotein Ib mutant)	Recombinant mutated "gain-of-function" GPIb (GPIbM) in the absence of ristocetin	Recombinant GPIbM using an ELISA plate or latex or magnetic beads
Binding to a monoclonal antibody to the GPIb site)	Binding of a specific monoclonal antibody to the VWF binding site for GPIb	Antibody that is specific for the GPIb binding site in VWF
VWF activity: Collagen binding (VWF:CB)	VWF binding to collagen	Binding of patient plasma VWF to collagen-coated plates in an ELISA assay (usually type I or type III collagen)
VWF antigen (VWF:Ag)	VWF protein concentration measured by immunologic assays (does not imply functional activity)	Immunologic assay using ELISA, RIA, or latex beads
VWF multimer analysis	Distribution of VWF multimers as visualized in gels	Electrophoresis in low concentration agarose gel and visualization using a monospecific antibody to VWF
Ristocetin-induced platelet aggregation (RIPA)	Ability of patient's VWF to bind to platelets in the presence of suboptimal concentrations of ristocetin	Platelet aggregation using patient's platelet-rich plasma and low concentrations of ristocetin (less than required in VWF:RCo)
VWF activity:VWF antigen ratio (VWF:Act/VWF:Ag)	Comparison of functional activity of VWF with its protein concentration	Ratio of measured levels of VWF:Act to VWF:Ag (a ratio of <0.7 suggests type 2A, 2B, or 2M)
Factor VIII activity:VWF:Ag ratio (FVIII/VWF:Ag)	Comparison of factor VIII activity to VWF antigen	Ratio of measured levels of FVIII to VWF:Ag (a low level suggests type 2N)

von Willebrand factor is a multimeric glycoprotein that promotes platelet adhesion to collagen and platelet aggregation. VWF also acts as a carrier protein for coagulation factor VIII in plasma. Ristocetin is an antibiotic (no longer in clinical use) that induces VWF binding to platelet glycoprotein Ib (GPIb), which in turn causes platelets to aggregate. Refer to UpToDate for information on how these tests are used and interpreted in the patient evaluation.

VWD: von Willebrand disease; VWF: von Willebrand factor; ELISA: enzyme-linked immunosorbent assay; RIA: radioimmunoassay.

Adapted from: The National Heart, Lung, and Blood Institute. The Diagnosis, Evaluation, and Management of Von Willebrand Disease. Bethesda, MD: National Institutes of Health Publication 08-5832, December 2007.

Graphic 73391 Version 5.0

خرید پکیج

Assays used for diagnosing von Willebrand disease (VWD)