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Test Code VWFACT von Willebrand Factor Activity

Specimen Type

Blood (plasma)

Preferred Collection Container

BLUE

Collection Volume

2.7 mL in 2.7 mL tube

Minimum Collection Volume

2.7 mL in 2.7 mL tube

Collection Instructions

Routine venipuncture. If multiple tests are being drawn, draw coagulation studies last. If only coagulation studies are being drawn, draw 1-2 mL into another Vacutainer, discard and then collect coagulation specimen. This collection procedure avoids contamination of the specimen with tissue thromboplastins. A special tube should be obtained from the laboratory for hematocrits over 55%. Specimens should be transported as soon as possible to the Clinical Laboratory.

Rejection Criteria

Specimens that are clotted, hemolyzed, diluted with IV fluid, received unfrozen more than 4 hours after collection, insufficient volume, improperly labelled, not double spun (not platelet poor).

Specimen Storage and Stability

Freeze double spun aliquots within 4 hours after collection. Samples may be frozen at -20° C for up to 2 weeks or at -70° C for up to six months.

Turn Around Time

7-10 days.

Lab Department

Hematology

Alias

von Willebrand Factor Assay, Ristocetin cofactor

Ordering Info

NOTE: Collection of blood for coagulation testing through indwelling catheters that have been flushed with heparin should be avoided, if possible. If specimen is drawn through an indwelling catheter, the line should be flushed with 5 ml saline and the first 5 ml of blood or six times the deadspace volume of the catheter being used should be discarded. Proper collection and handling of specimens is critical.

Acceptable Collection Container

BLUE (3.2% buffered sodium citrate)

Transfer Instructions

Centrifuge samples at 1500 g for 15 minutes. Remove plasma with plastic transfer pipette and place into a plastic tube. Centrifuge the transferred plasma at 1500 g for 15 minutes. Transfer plasma to new plastic tubes (1 mL aliquots per tube) and freeze.

Day(s) and Time(s) Performed

Monday through Friday, 7am to 3pm

STAT Availability

Yes-must call Hematology to make arrangements