Clinics and Departments

Laboratory Services

Lab Dept:


Test Name:


General Information

Lab Order Codes:



See individual test listings, links can be found under Reference Range

CPT Codes:

85240 - Clotting; factor VIII (AHG), one stage
85245 - Factor VIII vW Factor, Ristocetin cofactor
85246 – Factor VIII vW antigen factor

Test Includes:

Factor VIII, Ristocetin Cofactor and von Willebrand antigen reported as a % and Ristocetin Cofactor:VW Antigen Ratio.

A specimen will be held for possible multimer analysis, please contact Pathology at 612- 813- 6711 for consultation. Tubes will be held for one month.


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:

Daily, 24 hours

Turnaround Time:

3 – 5 Days, performed Tuesday and Thursday

Special Instructions:

See Patient Preparation

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 tubes

Draw Volume:

8.1 mL blood (into three 2.7 mL tubes) Minimum: 5.4 mL blood (into two 2.7 mL tubes)

Processed Volume:

2.7 mL (Minimum: 1.8 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: Centrifuge specimen, remove plasma sample taking care not to disturb buffy coat. Perform a second spin after removing plasma from the original collection containers. Aliquot into two screw top plastic vials (Minimum: 0.5 mL in each). Store frozen at -70 degrees C (one vial in “VWS to be completed” cup and the other in the “von Willebrand Multimer Testing” cup for potential multimer analysis) temperatures.

Patient Preparation:

No Heparin for 2 days prior to testing.

Sample Rejection:

Improper tube; clotted sample; underfilled tube; mislabeled or unlabeled specimens


Reference Range:

See individual tests for specific reference ranges:
von Willebrand Antigen

Factor VIII Assay

Ristocetin Cofactor

For further interpretation of results or questions regarding Multimer analysis, please contact Pathology at 612- 813- 6711.

Critical Values:



See individual test listings, links can be found under Reference Range


See individual test listings, links can be found under Reference Range


See individual test listings, links can be found under Reference Range


5/24/2010: Tubing patient specimens is no longer prohibited.
9/15/2014: Added Off Campus collection info.
8/2/15: Days performed updated

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