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Test Code VWACT von Willebrand Factor Activity, Plasma


Advisory Information


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 von Willebrand activity.



Specimen Required


See Coagulation Studies in Special Instructions: Guidelines for Specimen Handling and Processing.

 

Specimen Type: Platelet-poor plasma

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

Submission Container/Tube: Polypropylene vial

Specimen Volume: 2 mL in 2 vials each containing 1 mL

Collection Instructions:

1. Specimen must be drawn prior to factor replacement therapy.

2. Centrifuge, remove plasma, and centrifuge plasma again.

3. Freeze plasma immediately (no longer than 4 hours after collection) at -20° C or ideally, ≤-40 degrees C.

4. 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 (LIA)

Reporting Name

von Willebrand Factor Activity, P

Specimen Type

Plasma Na Cit

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% 

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%.

Day(s) and Time(s) Performed

Monday through Saturday

Performing 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 U.S. 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.