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Test Code VWF von Willebrand Factor Functional, Risto Cofactor (GPIb Binding) Activity

Specimen Type

Plasma

Container/Tube

Light blue top tube, 3.2% sodium citrate

Offsite Collection Instructions

Whole blood sample must arrive in the laboratory within
three hours of specimen collection.

 

If transport time exceeds three hours, follow centrifugation
instructions:

  • Samples must be centrifuged at >2500 x g for 10 minutes
    at room temperature.
  • Carefully remove the plasma from the cells using a plastic
    transfer pipette avoiding the buffy coat.
  • Aliquot removed plasma into 2 plastic tubes containing a
    minimum of 500 uL of specimen in each tube.
  • The plasma samples must then be frozen at -20 C.
  • Once solidly frozen, they must be shipped on dry ice.
    Samples that have thawed in transit will be rejected.

Note: For clients who do not have access to dry ice DO
NOT freeze the specimen. Follow the centrifugation instructions and
send fresh plasma or send whole blood sample. It now becomes
vital that the specimen arrives in the lab within three hours of
collection.

Turnaround Time

Monday-Friday 12 hours

Test Includes

vWF, Risto Cofactor (GPIb Binding) Activity

Preferred Volume

1 mL

UCMC Collection Instructions

Specimens may be collected and sent to the laboratory at any
time.

Test can be added on to an existing order up to 4 hours
following the time of blood draw.

Additional Information

All 3.2% sodium citrate light blue top tubes require a ratio
of 9 parts blood to 1 part anticoagulant (example: a 3.0 mL tube
requires 2.7 mL blood added to 0.3 mL of anticoagulant).

Fee Code

30585245

Test Usage

Functional assay of vWF binding to platelets

Synonyms

Ristocetin cofactor, vWF functional, von Willebrand Factor

STAT Turnaround Time

n/a

Specimen Minimum Volume

0.5 mL

DAY(S) AND TIME(S) PERFORMED

Sample may be collected 24/7. Test is performed Monday
Friday, 8:00 am  2:00 pm

STAT DAY(S) AND TIME(S) PERFORMED

Not Available

CPT

85245

Method Name

Agglutination

Reference Values

55-165%

Reject Due To

Specimens that have wrong ratio of blood to anticoagulant
(fill volume) clotted or grossly hemolyzed.