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HelpTest ID VWAG von Willebrand Factor Antigen, Plasma
Useful For
von Willebrand factor (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)
Monitoring therapeutic efficacy of treatment with DDAVP (desmopressin) or VWF concentrates in patients with VWD
Special Instructions
Method Name
Automated Latex Immunoassay (LIA)
Reporting Name
von Willebrand Factor Ag, PSpecimen Type
Plasma Na CitSee Coagulation Studies in Special Instructions.
Specimen Type: Platelet-poor plasma
Collection Container/Tube: Light-blue top (citrate)
Submission Container/Tube: Plastic vial
Specimen Volume: 1 mL
Collection Instructions:
1. Spin down, remove plasma, and spin plasma again.
2. Freeze specimen immediately at ≤-40° C, if possible.
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.
3. Tests for VWFX / von Willebrand Factor Activity, Plasma and F8A / Coagulation Factor VIII Activity Assay, Plasma are recommended in conjunction with von Willebrand antigen.
Forms: If not ordering electronically, complete, print, and send a Coagulation Test Request Form (T753) with the specimen (http://www.mayomedicallaboratories.com/it-mmfiles/coagulation-test-request-form.pdf)
Specimen Minimum Volume
0.5 mL
Specimen Stability Information
| Specimen Type | Temperature | Time |
|---|---|---|
| Plasma Na Cit | Frozen | 14 days |
Clinical Information
The 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 VWD 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
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.
Cautions
Lipemic specimens may lead to an underestimation of the von Willebrand factor (VWF) level.
The presence of rheumatoid factor may lead to an overestimation of the VWF level.
VWF is an acute-phase reactant and may be elevated above baseline in association with a variety of conditions including inflammation, stress, exercise, liver disease, pregnancy or estrogen therapy. Baseline VWF levels also increase with aging. These conditions may obscure diagnosis of the milder forms of von Willebrand disease (VWD). Repeat testing may be indicated.
Low normal levels of VWF antigen do not exclude possible diagnosis of VWD.
Borderline low or slightly decreased levels of VWF antigen may be observed in clinically normal individuals of blood group "O."
Day(s) Performed
Monday through Saturday
Report Available
1 dayPerforming Laboratory
Mayo Medical Laboratories in Rochester
Test Classification
This test has been cleared or approved by the U.S. Food and Drug Administration and is used per manufacturer's instructions. Performance characteristics were verified by Mayo Clinic in a manner consistent with CLIA requirements.CPT Code Information
85246