von Willebrand Factor Activity, Plasma
Use
This test is used for the diagnosis of von Willebrand disease (VWD) and distinguishing between VWD subtypes or from hemophilia A. It is also important for monitoring the therapeutic efficacy of treatment with DDAVP (desmopressin) or VWF concentrates in patients with VWD.
Special Instructions
The test is most effective when combined with the measurement of von Willebrand factor antigen and factor VIII coagulant activity. Ideally, it should be performed as part of a panel of tests with reflexive testing and interpretive reporting.
Limitations
The measurement of von Willebrand factor (VWF) activity alone has limited diagnostic value. The diagnosis of VWD requires comprehensive clinical and laboratory evaluation. Assay results must be integrated with assays of VWF antigen and factor VIII coagulant activity for optimal clinical utility and diagnostic efficiency. Certain factors like high triglycerides, hemoglobin, or bilirubin levels can affect the test results, and the presence of human antimouse antibodies may cause interference in immunoassays.
New York Approved
Methodology
Immunoassay (Latex Immunoassay)
Biomarkers
LOINC Codes
- 68324-3
- 68324-3
Result Turnaround Time
1-3 days
Related Documents
For more information, please review the documents below
Specimen
Plasma
Volume
2 mL in 2 vials each containing 1 mL
Minimum Volume
0.5 mL
Container
Light-blue top (3.2% sodium citrate); Submission Container/Tube: Plastic vial (polypropylene preferred)
Collection Instructions
Specimen must be collected prior to factor replacement therapy. Centrifuge, transfer all plasma into a polypropylene vial, and centrifuge plasma again. Aliquot plasma (1-2 mL per aliquot) into 2 separate polypropylene vials leaving 0.25 mL in the bottom of centrifuged vial. Freeze plasma immediately at -20 degrees C or, ideally, <=-40 degrees C. Send specimens in the same shipping container. Double-centrifuged specimen is critical for accurate results as platelet contamination may cause spurious results.
Storage Instructions
Freeze plasma immediately (ideally at <=-40 degrees C).
Causes for Rejection
Gross hemolysis, gross lipemia, gross icterus
Stability Requirements
| Temperature | Period |
|---|---|
| Frozen | 14 days |