Laboratory Medicine Program

von Willebrand Factor (vWF) Activity
(Ristocetin CoFactor Activity)

Clinical Decription:
von Willebrand factor (vWF) activity is measured as part of the vWF complex study that includes factor VIII activity, vWF activity and vWF antigen. vWF is a large multimeric hemostastic protein synthesized in the endothelial cells and released into the vascular space. It has multiple functions including carrier protein for factor VIII, platelet agglutination and high shear platelet-surface adhesion. The diagnosis and characterization of vWF disease includes vWF complex study and vWF multimer studies.

Method: Turbidimetric; Siemens Sysmex CS-5100

Component Tests Used: Factor VIII, vWF Activity, vWF Antigen

Reference Ranges Used:
0.40 - 1.50 IU/mL

Specimen Type: Citrated plasma
Collected In: 3.2% Sodium Citrate
Volume: 2.0 mL (minimum: 2.0 mL)

Shipping: Send frozen on dry ice.

Special Instructions: Patient should be fasting, if possible. The specimen must be double-centrifuged to obtain a platelet-poor plasma specimen (Plt <10x10E9/L): 1. Immediately centrifuge specimen at 1500xG for 10 minutes. 2. Separate the plasma from the platelet/buffy coat and transfer into a clean plastic tube. 3. Centrifuge the separated plasma at 1500xG for 10 minutes. 4. Transfer 1.0 to 2.0 mL of the double-centrifuged plasma into a clean plastic tube, leaving approx. 200 uL for discard. 5. Freeze plasma aliquot immediately for storage. Maintain frozen for shipping and handling. Refrigerated storage is NOT acceptable.

Testing Schedule(s): Weekly.

Turnaround Time: 5 days

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For more information, call 416.340.5227 or 1.866.865.5227

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