Name: Von Willebrand Factor Ag
Test Name: Von Willebrand Factor Ag
Health Link Test Code: XVWFAG
LIS Test Code: VWF-AG
CPT Code(s): 85246
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: 4 - 10 days.
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 factors 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
1 month at -20°C
Sample Analyzed: Plasma
Testing Volume: 1 mL
Pediatric Testing Volume: 0.5 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 antigen (vWF) levels than those of non-O blood groups. Normal individuals of blood group "O" may have plasma vWF antigen levels as low as 45-55% NPP. The lower limit of the reference interval for individuals of non-O blood groups may be 60-70% NPP. Plasma vWF antigen levels may be increased in acute phase reaction conditions.
The presence of rheumatoid factor leads to a falsely elevated vWF level. The extremely rare presence of anti-bovine albumin and/or anti-rabbit antibodies in certain subjects may give falsely elevated test results. All vWF antigen results should be interpreted in the context of the clinical setting for each patient.