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HelpTest Code VWACT von Willebrand Factor Activity, Plasma
Ordering Guidance
This activity assay is most effective when it is combined with measurement of von Willebrand factor antigen and factor VIII coagulant activity, preferably as a panel of tests with reflexive testing and interpretive reporting. See AVWPR / von Willebrand Disease Profile, Plasma.
Additional Testing Requirements
Tests for F8A / Coagulation Factor VIII Activity Assay, Plasma and VWAG / von Willebrand Factor Antigen, Plasma are recommended in conjunction with this test (von Willebrand activity).
Specimen Required
Specimen Type: Platelet-poor plasma
Collection Container/Tube: Light-blue top (3.2% sodium citrate)
Submission Container/Tube: Plastic vial (polypropylene preferred)
Specimen Volume: 2 mL in 2 vials each containing 1 mL
Collection Instructions:
1. Specimen must be collected prior to factor replacement therapy.
2. For complete instructions, see Coagulation Guidelines for Specimen Handling and Processing.
3. Centrifuge, transfer all plasma into a polypropylene vial, and centrifuge plasma again.
4. Aliquot plasma (1-2 mL per aliquot) into 2 separate polypropylene vials leaving 0.25 mL in the bottom of centrifuged vial.
5. Freeze plasma immediately (no longer than 4 hours after collection) at -20° C or, ideally, ≤-40° C.
6. Send specimens in the same shipping container.
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.
Useful For
Diagnosis of von Willebrand disease (VWD) and differentiation of VWD subtypes or differentiation of VWD from hemophilia A
Monitoring therapeutic efficacy of treatment with DDAVP (desmopressin) or VWF concentrates in patients with VWD
Reflex Tests
| Test ID | Reporting Name | Available Separately | Always Performed |
|---|---|---|---|
| RIST | Ristocetin Cofactor, P | No | No |
Testing Algorithm
If von Willebrand factor activity is less than 55%, then the von Willebrand factor ristocetin cofactor activity assay will be performed at an additional charge.
Special Instructions
Method Name
Latex Immunoassay
Reporting Name
von Willebrand Factor Activity, PSpecimen Type
Plasma Na CitSpecimen Minimum Volume
0.5 mL
Specimen Stability Information
| Specimen Type | Temperature | Time | Special Container |
|---|---|---|---|
| Plasma Na Cit | Frozen | 14 days |
Reference Values
55-200%
Normal, full-term newborn infants may have mildly increased levels which reach adult levels by 90 days postnatal. Healthy, premature infants (30-36 weeks gestation) may have increased levels that reach adult levels by 180 days.
Note: Individuals of blood group "O" may have lower plasma von Willebrand factor (VWF) activity than those of other ABO blood groups, such that apparently normal individuals of blood group "O" may have plasma VWF activity 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%.
Interpretation
von Willebrand factor (VWF) activity is reduced in parallel with VWF antigen in von Willebrand disease (VWD), except in types 2A, 2B, and 2M, and some cases of acquired von Willebrand syndrome (AVWS) in which the VWF activity is disproportionately decreased relative to the level of VWF antigen.
The VWF activity may be decreased in congenital VWD or AVWS that may be associated with are variety of disorders including monoclonal gammopathies, lymphoproliferative disorders, autoimmune disorders, hypothyroidism, severe aortic stenosis, left ventricular assist device, and arteriovenous malformation.
The VWF activity may be increased in association with pregnancy or estrogen use (including oral contraceptives), acute (acute-phase reactant) or chronic inflammation, exercise or stress, liver disease, vasculitis, and thrombotic thrombocytopenic purpura/hemolytic uremic syndrome (TTP/HUS). Such increases in VWF activity may obscure the laboratory diagnosis of mild VWD.
Clinical Reference
1. Montgomery RR. Structure and function of von Willebrand factor. In: Colman RW, Hirsh J, Marder VJ, et al, eds. Hemostasis and Thrombosis: Basic Principles and Clinical Practice. 4th ed. Lippincott Williams and Wilkins; 2001:249-274
2. Sadler JE, Lillicrap DL. von Willebrand disease: diagnosis, classification, and treatment. In: Marder VJ, Aird WC, Bennett JS, Schulman S, White II GC, eds. Hemostasis and Thrombosis: Basic Principles and Clinical Practice. 6th ed. Lippincott Williams and Wilkins; 2013:670-683
3. Favaloro EJ and Lippi G. eds. Hemostasis and Thrombosis, Methods and Protocols. 1st ed. Humana Press; 2017
4. Salem RO, Van Cott EM. A new automated screening assay for the diagnosis of von Willebrand Disease. Am J Clin Pathol. 2007;127(5):730-735
5. Favaloro EJ, Lippi G, eds. Hemostasis and Thrombosis: Methods and Protocols. Humana Press; 2017.
Day(s) Performed
Monday through Saturday
Report Available
1 to 3 daysPerforming Laboratory
Mayo Clinic Laboratories in Rochester
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
85397
LOINC Code Information
| Test ID | Test Order Name | Order LOINC Value |
|---|---|---|
| VWACT | von Willebrand Factor Activity, P | 68324-3 |
| Result ID | Test Result Name | Result LOINC Value |
|---|---|---|
| VWACT | von Willebrand Factor Activity, P | 68324-3 |
Forms
If not ordering electronically, complete, print, and send a Coagulation Test Request (T753) with the specimen.