Name: Von Willebrand Factor Activity
Test Name: Von Willebrand Factor Activity
Health Link Test Code: HCVWFACT
LIS Test Code: VWFACT
CPT Code(s): 85245
The von Willebrand Factor Activity reflects the binding of a monoclonal antibody to a confirmation epitope of the von Willebrand antigen.
Days Performed: Mon-Fri, dayshift - day varies. Specimens are accepted at any time. Testing required during off hours must be approved by a Coagulation physician. Call 263-5005 before collection.
In-Lab Turnaround Time: 1 - 2 weeks.
Stat In-Lab Turnaround Time: 1 day.
Collection Container: Light blue top (3.2% NaCitrate)
Do NOT draw through a line containing heparin. The venipuncture MUST be atraumatic to avoid hemolysis and contamination with tissue factor and platelets. Tube must be allowed to fill completely. Indicate if patient is receiving anticoagulant(warfarin/ Heparin/Vitamin K antagonist), direct thrombin inhibitor or fibrinolytic agent therapy and duration.
Collection Volume: Full 3.5 mL tube
Pediatric Collection Volume: Pediatric tube filled to fill mark
4 hours on spun tube
2 weeks at -20°C; 6 months at -70°C
Sample Analyzed: Plasma
Testing Volume: 2 mL
Pediatric Testing Volume: 1 mL
Centrifuge specimen to yield platelet poor plasma (platelet count should be less than 10 K/uL). Separate plasma and transfer to plastic tube or vial. Freeze plasma within 4 hours of collection at -20°C or below.
Transport whole blood specimen at room temperature to UWHC Hospital Laboratory within 4 hours of collection. See Specimen Processing for instructions if transport criteria are not met. Transport frozen plasma aliquot on dry ice to UWHC Hospital Laboratory.
Hemolyzed specimens, clotted specimens, partially filled tubes and whole blood specimens greater than 4 hours old when received by the laboratory are not acceptable.
0 days and up: 55-200 %NPP
Interpretation Type: Reference Interval
Individuals of blood group "O" may have lower plasma von Willebrand factor activity levels than those of non-O blood groups. Normal individuals of blood group "O" may have plasma vWF activity levels as low as 40-50% NPP. The lower limit of the reference interval for individuals of non-O blood groups may be 60-70% NPP.
The presence of rheumatoid factor, anti-bovine IgG antibodies and/or monoclonal gammopathy may give falsely elevated test results. All vWF activity results should be interpreted in the context of the clinical setting for each patient.