Clinics and Departments

Laboratory Services

Lab Dept:


Test Name:


General Information

Lab Order Codes:



Factor VIIIR:Ag; Factor VIII Related Antigen; VIIIR Antigen; vWF Ag; Factor VIII Activity; von Willebrand Factor Immunodeficiency Assay

CPT Codes:

85246 – Factor VIII vW antigen factor

Test Includes:

Von Willebrand antigen reported as a %.


Test Indications:

Useful for diagnosis (or exclusion) of von Willebrand’s disease or trait.

Lab Testing Section:

Coagulation (Minneapolis Campus)

Phone Numbers:

MIN Lab: 612-813-6280

STP Lab: 651-220-6550

Test Availability:

Twice Weekly (Tuesday and Friday)

Turnaround Time:

3 – 5 Days

Special Instructions:

See Patient Prepartion

Deliver immediately to the laboratory at room temperature. Indicate when specimen is drawn from a line or a heparin lock.


Specimen Type:

Whole blood


Light Blue (Buffered Na Citrate 3.2%) top tube

Draw Volume:

2.7 mL blood

Processed Volume:

0.9 mL plasma


● A clean venipuncture is essential, avoid foaming.
● Entire sample must be collected with single collection, pooling of sample is unacceptable.
● Capillary collection is unacceptable.
● Patient’s with a hematocrit level >55% must have a special tube made to adjust for the hematocrit; contact lab for a special tube.
● Mix thoroughly by gentle inversion. Deliver immediately to the laboratory at room temperature via courier or pneumatic tube.

Off campus collections:
● Must be tested within 4 hours.
● Do not refrigerate.
● If not received in our lab within 4 hours of collection, sample must be centrifuged and *platelet-poor plasma removed from cells and transferred to an aliquot tube being careful not to disturb the cell layer. Centrifuge the plasma a second time and transfer into a clean aliquot tube being careful not to include any residual platelets on the bottom of the tube. Freeze at -20C and deliver to the lab on dry ice within 2 weeks.
*Validation of your lab’s centrifuge for platelet poor plasma is required.

Special Processing:

Lab Staff: All testing will be performed in Minneapolis.

St. Paul Lab: Send whole blood specimens to Mpls for processing via courier. Must be processed within 4 hours of collection. Contact Mpls prior to sending.

Mpls Lab: Spin sample collected in blue top tube for 5 minutes on the Stat Spin centrifuge, remove plasma and transfer to a 4 mL BCS sample cup. Spin remaining plasma again for 5 minutes in the Stat Spin Centrifuge. Transfer plasma to a new BCS sample cup for analysis leaving approximately 200 mcL in the bottom of the original cup to discard.

Patient Preparation:

No Heparin for 2 days prior to testing.

Sample Rejection:

Clotted sample; underfilled tube; overfilled tube; mislabeled or unlabeled specimens


Reference Range:


Range (%):

Full Term Infants

Day 1

50 – 207%

Day 5

50 – 254%

Day 30

50 – 246%

Day 90

50 – 206%

Day 180

50 – 197%


1 – 5 years

60 – 120%

6 – 10 years

44 – 144%

11 – 16 years

46 – 153%


50 – 158%

Critical Values:



This test measures the quantity of von Willebrand von Willebrand Antigen, factor protein not functional activity. Antigen and activity values are increased in patients who are pregnant or are taking oral contraceptives.


Measurement of vonWillebrand’s factor protein i.e., antigen by the immuno-turbimetric method. Patient dilutions are compared to a known set of standard dilutions and a percentage is determined.


Harmening DH (1997) Clinical Hematology and Fundamentals of Hemostasis


5/24/2010: Tubing patient specimens is no longer prohibited.
12/14/2010: Updated processing information.
9/15/2014: Added Off Campus collection info.

  Lab Test Directory
    Microbiology/ Virology
    Other Fluids
    Transfusion Services

  Search Lab Test Directory
    List All Documents

  Lab Staff

  E-mail Lab Services