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Test Code VWAG von Willebrand Factor Antigen, Plasma

Reporting Name

von Willebrand Factor Ag, P

Useful For

Diagnosis of von Willebrand disease (VWD) and differentiation of VWD subtype (in conjunction with von Willebrand factor ristocetin cofactor activity and factor VIII coagulant activity)

 

Differentiation of VWD from hemophilia A (in conjunction with factor VIII coagulant assay)

 

Monitoring therapeutic efficacy of treatment with DDAVP (desmopressin) or von Willebrand factor concentrates in patients with VWD

Performing Laboratory

Mayo Clinic Laboratories in Rochester

Specimen Type

Plasma Na Cit


Ordering Guidance


For optimum clinical utility and diagnostic efficiency, this test's results generally must be used together with the results of the von Willebrand factor ristocetin cofactor activity and factor VIII coagulant activity tests. The diagnosis of von Willebrand disease requires a combination of clinical and laboratory information. For a streamlined approach to testing, a panel of tests with reflexive testing and interpretive reporting is recommended. See AVWPR / von Willebrand Disease Profile, Plasma.



Additional Testing Requirements


VWACT / von Willebrand Factor Activity, Plasma and F8A / Coagulation Factor VIII Activity Assay, Plasma are recommended in conjunction with this test (von Willebrand antigen).



Specimen Required


Specimen Type: Platelet-poor plasma

Collection Container/Tube: Light-blue top (3.2% sodium citrate)

Submission Container/Tube: Plastic vial

Specimen Volume: 1 mL

Collection Instructions:

1. For complete instructions, see Coagulation Guidelines for Specimen Handling and Processing.

2. Centrifuge, transfer all plasma into a plastic vial, and centrifuge plasma again.

3. Aliquot plasma into a plastic vial, leaving 0.25 mL in the bottom of centrifuged vial.

4. Freeze plasma immediately (no longer than 4 hours after collection) at -20° C or, ideally, less than or equal to -40° C.

Additional Information:

1. Double-centrifuged specimen is critical for accurate results as platelet contamination may cause spurious results.

2. Each coagulation assay requested should have its own vial.


Specimen Minimum Volume

0.5 mL

Specimen Stability Information

Specimen Type Temperature Time Special Container
Plasma Na Cit Frozen 14 days

Reference Values

55-200%

Note: Individuals of blood group "O" may have lower plasma von Willebrand factor (VWF) antigen than those of other ABO blood groups, such that apparently normal individuals of blood group "O" may have plasma VWF antigen as low as 40% to 50%, whereas the lower limit of the reference range for individuals of other blood groups may be 60% to 70%.

Children: Neonates, infants, and children have normal or mildly increased plasma VWF antigen, with respect to the adult reference range.

Day(s) Performed

Monday through Saturday

Test Classification

This test has been modified from the manufacturer's instructions. Its performance characteristics were determined by Mayo Clinic in a manner consistent with CLIA requirements. This test has not been cleared or approved by the US Food and Drug Administration.

CPT Code Information

85246

Clinical Information

von Willebrand factor (VWF) is a multimeric adhesive glycoprotein that is important for platelet-platelet and platelet-vessel hemostatic interactions. In addition, plasma VWF serves as a carrier protein for coagulation factor VIII, stabilizing its procoagulant activity. VWF circulates in the blood in 2 distinct compartments; plasma VWF mainly reflects VWF synthesis and release from vascular endothelial cells and platelet VWF (about 10% of the blood VWF) reflects VWF synthesis by bone marrow megakaryocytes with storage primarily in the alpha granules of circulating platelets. VWF antigen measurement assesses the mass of plasma VWF protein but does not reflect VWF functions or platelet VWF. The major function of VWF (mediating platelet-platelet or platelet-vessel interaction) is most commonly assessed by measurement of plasma ristocetin cofactor activity.

 

Decreased VWF antigen may be seen in:

-Congenital von Willebrand disease

-Acquired von Willebrand disease that may be associated with monoclonal gammopathies, lymphoproliferative disorders, autoimmune disorders, and hypothyroidism

 

Increased VWF antigen may be seen in association with:

-Pregnancy and/or estrogen use

-Inflammation (acute-phase reactant)

-Exercise or stress

-Liver disease

-Vasculitis

-Thrombotic thrombocytopenic purpura/hemolytic uremic syndrome

 

Note: VWF antigen measurement is most effective when it is combined with measurement of VWF ristocetin cofactor activity and factor VIII coagulant activity, preferably as a panel of tests with reflexive testing and interpretive reporting. Within this context, VWF antigen measurement can be useful for:

-Diagnosis of von Willebrand disease (VWD) and differentiation of VWD subtype

-Differentiation of VWD from hemophilia A (in conjunction with factor VIII coagulant assay)

Report Available

1 to 3 days

Reject Due To

Gross hemolysis Reject
Gross lipemia Reject
Gross icterus Reject

Method Name

Latex Immunoassay (LIA)

Forms

If not ordering electronically, complete, print, and send a Coagulation Test Request (T753) with the specimen.