Test Directory

von Willebrand Factor Activity, Plasma

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Updated Test Information:

Test Description
von Willebrand Factor Activity, Plasma
Synonym(s)
von Willebrand Factor Activity
Test ID
VWACT
General Information
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
Specimen Type
Plasma
Specimen Requirements
Light Blue
Specimen Collection / Processing Instructions
Light Blue - 2 mL in 2 vials each containing 1 mL. 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 degrees C or ideally, less than or =-40 degrees C. 4. Send specimens in the same shipping container.
Stability
Frozen 14 days
Unacceptable Specimen Conditions
Gross hemolysis Reject
Gross lipemia Reject
Gross icterus Reject
Methodology
Latex Immunoassay (LIA)
Estimated TAT
3-7 days
Testing Schedule
Monday-Saturday
CPT Code(s)
85397
Minimum Sample Volume
0.5 mL
Reference Range

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%.

Reflex Conditions
RIST Ristocetin Cofactor
Performing Lab
Mayo
LOINC Code(s)
68324-3