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Von Willebrand Disease (VWD)
Part 3: VWF Activity Assay

A New von Willebrand Factor Activity Assay and Testing Algorithm



June 2011

Beyond Hot Topic is an opportunity for viewers to submit questions to the Hot Topic presenter. The opportunity to submit questions for this topic is now closed.

The following questions were submitted by viewers and answered by the presenter, Dong Chen, MD, PhD, Co-director of the Special Coagulation Laboratory. Questions are presented as submitted (unedited).

  1. What if a physician insists on having a Ristocetin Cofactor test performed?

    The ristocetin cofactor test (VWF:RCo) is a reflex test that will be performed if the VWF activity by latex-immunoassay is below the lower limit of the normal range (55 IU/dL), or if there is any significant discrepancy among various results of VWF tests. Usually laboratory consultants/physicians will determine if VWF:RCo is needed or not. One example will be monitoring VWF-replacement therapy (such as humate-P etc.). Therefore, I would recommend to indicate that VWF:RCo test is preferred on the request form and also include available clinical information and physician contact phone number. By doing so, we may be able to better utilize our reflex VWF:RCo testing and resolve potential VWF-testing questions from the ordering physician.


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