VWF Inhibitor Assay: Reprise

Here is a little more on the laboratory detection of von Willebrand factor (VWF) inhibitors in acquired von Willebrand disease (aVWD). This was the subject of a July 22 note from Vilas Hiremath with a July 23 response from Kent Chapman.

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VWF Inhibitor Assay

Dear Sir,
I would like to know is there any kit for VWD inhibitor study.
with regards, Vilas Hiremath.

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Off-Label NovoSeven

Most transfusion services adopt a policy recommending Novo Nordisk’s recombinant activated factor VIIa (rFVIIa, NovoSeven®) in acute hemorrhage when conventional therapy; RBCs, frozen plasma, platelet concentrate, and cryoprecipitate fail to stop the bleeding. NovoSeven is FDA-cleared for prophylaxis or therapy in hemophilia A or B patients with inhibitors or people with congenital factor VII deficiency. When it is used to stop non-hemophilic bleeding in the operating or emergency room or on the battlefield, however, this is off-label. Several studies have implied that NovoSeven may trigger arterial or venous thrombosis when used in high-risk patients such as those with previous thrombotic disorders. The US legal system has seized on this information, and now the Sunday, May 16 Baltimore Sun alleges a criminal investigation of military usage in Iraq, placing Novo Nordisk and the Army in a defensive position. There is no question that NovoSeven rescues patients who are “going south” on the table. Many of us have witnessed abrupt turn-arounds in which patients stop bleeding, restore electrolyte balance, recover from hypothermia, and raise their blood pressure.Thirty-day outcomes, however, seem to indicate no significant long-term improvement. I’d like to hear from you, what is your institution’s policy regarding the use of NovoSeven, how successful is it, and have you personally witnessed clinical “rescues.”

Case Study: Neonatal Bleeding

Here is an interesting case study message from Boriana Parvez, a health care provider, location not provided.

I’m caring for a full-term female neonate currently two weeks old who presented at three days of life with bilateral subdural bleeds and an intraparenchymal bleed. Her initial prothrombin time (PT) and partial thromboplastin time (PTT) were 73 and 133 seconds, respectively, and platelets 23,000/uL. She was given fresh frozen plasma (FFP) and her PTT corrected to 24 but her PT remained 75 seconds. The platelet count corrected without therapy.

The next day her PT was still 75 seconds and PTT had risen to 133 seconds. Her fibrinogen was markedly reduced at 50 mg/dL. FFP corrected the fibrinogen and PTT but the PT remained 75 seconds. On this basis we speculated that she has a factor VII deficiency, but factors V, VII and X are all  normal. At this time she developed thrombocytosis at 1,500,000/uL.

We conducted a mixing study that normalized the PT, excluding the presence of inhibitors. Any thoughts on what is the diagnosis? Is a lab error possible?

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Automated Ristocetin Cofactor

Here is a question I received early in January from Elpidio Pena. I apologize to Elpidio for letting this one slip through the cracks.

George: our lab performs the ristocetin cofactor (VWF activity) assay using the traditional platelet aggregation method. We are planning to change instruments and one of the instruments we are considering performs the assay by ELISA (coated beads). Any advantages/disadvantages on the ELISA method? Any particular issue to consider with this method?

Thanks.
Elpidio Pena

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Wilate von Willebrand Factor Cleared

Gerald Sapp, University of Alabama at Birmingham transfusion service manager told Margaret Fritsma, MA SBB (ASCP)–who then told me–that Octapharma USA announced their human plasma-derived biological, Wilate® von Willebrand factor/coagulation factor VIII complex was cleared by the FDA 12/4/09. Click these links for Octapharma’s Wilate brochure and package insert.

Gerald wanted to know if anyone has experience with Wilate, and whether it is a valid substitute for Humate-P. I would also like to know if it can be monitored using the same methods, ristocetin cofactor (VWF:RCo) and factor VIII, as are used to monitor Humate-P. If you are using Wilate, please provide your information using the comments link. Thanks, Geo.

Fibrinogen Concentrate

Margaret G. Fritsma, MA (ASCP) SBB came home from the October 2009 American Association of Blood Banks (AABB) annual meeting in New Orleans with information of a new fibrinogen concentrate, RiaSTAP®, available from CSL Behring, King of Prussia, PA. RiaSTAP® has been previously approved for therapy in several Northern European countries. This is a plasma-derived product for treating afibrinogenemia and hypofibrinogenemia, but not dysfibrinogenemia, and its clinical efficacy is based upon a thromboelastography surrogate, maximum clot firmness (MCF).

If anyone has been using RiaSTAP®, I’d like to collect some anecdotes about its efficacy and learn whether the standard Klauss fibrinogen assay is an effective monitor. Geo.

Von Willebrand Factor Reference Ranges

Some von Willebrand questions from “Charlie” in Edmonton:

What are the reference ranges for von Willebrand factor (VWF) antigen and for factor VIII? And what might cause these values to increase in a person who was originally thought to have a problem with being able to clot?

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