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Test Code LAB1235529 von Willebrand Factor Activity, Plasma

Important Note

Mayo's test code: VWACT


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.

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

Reject Due To

Gross hemolysis Reject
Gross lipemia Reject
Gross icterus Reject

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%.

Supportive Data

This assay (HemosIL von Willebrand factor [VWF] activity) performed on the ACL TOP instrument demonstrates the following validation characteristics: intra- and interassay precision (CV) are less than or equal to 10%; the lower limit of detection is 3%; with excellent linearity (r [2]=0.999) up to 1,000%. For apparently healthy subjects (n=368) and for patients with type 1 von Willebrand disease (VWD) (n=57), the HemosIL VWF activity assay correlates well with the platelet agglutination assay for VWF ristocetin cofactor (RCo) activity. For patients with type 2A, 2B, or 2M VWD (independently determined by VWF:RCo, VWF antigen, and plasma VWF multimer analysis), the sensitivity and specificity of the HemosIL VWF activity is 100%. Moreover, compared to VWF:RCo, the HemosIL VWF activity is more sensitive to loss of the highest molecular weight VWF multimers among patients with AVWS. This is also reflected in type 3 VWD patients receiving Humate P therapy where the VWF activity is 10% to 20% lower than the VWF:RCo. Plasma VWF multimer analysis of these patients revealed loss of the highest molecular weight VWF multimers. Finally, a VWF activity:VWF antigen ratio greater than 0.8 reliably excludes congenital type 2A and 2B VWD, and AVWS (including loss of the highest VWF multimers due to left ventricular assist device).

Day(s) Performed

Monday through Saturday

Report Available

1 to 3 days

Specimen Retention Time

7 days

Performing Laboratory

Mayo Clinic Laboratories in Rochester

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.