von Willebrand Factor (vWF) Ag

If the patient's hematocrit exceeds 55%, the volume of citrate in the collection tube must be adjusted. Refer to Coagulation Collection Procedures for directions.

086280

Antigenic Factor VIII; CRM Assay; von Willebrand Factor Antigen; vWF Antigen

Plasma, FROZEN

2 mL

Blood should be collected in a blue-top tube containing 3.2% buffered sodium citrate.(1) Evacuated collection tubes must be filled to completion to ensure a proper blood-to- anticoagulant ratio.(2,3) The sample should be mixed immediately by gentle inversion at least six times to ensure adequate mixing of the anticoagulant with the blood. A discard tube is not required prior to collection of coagulation samples unless the sample is collected using a winged (butterfly) collection system. With a winged blood collection set a discard tube should be drawn first to account for the dead space of the tubing and prevent under-filling of the evacutated tube.(4,5) When noncitrate tubes are collected for other tests, collect sterile and nonadditive (red-top) tubes prior to citrate (blue-top) tubes. Any tube containing an alternative anticoagulant should be collected after the blue-top tube. Gel-barrier tubes and serum tubes with clot initiators should also be collected after the citrate tubes. To avoid delays in turnaround time when requesting multiple tests on frozen samples, please submit separate frozen specimens for each test requested. Print and use the Specimen Collection Bulletin as a tube-filling guide.

Blue-top (sodium citrate) tubes

FREEZE

Gross hemolysis; clotted specimens; specimens that have thawed in transit; improperly labeled specimen.

Daily 1st shift