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VON WILLEBRAND FACTOR (VWF) ACTIVITY, PLASMA
MessageThis test replaced the ristocetin cofactor assay for determining vWF activity levels.
Test Code
LAB335
CPT Codes
85397, LOINC: 68324-3
Preferred Specimen
One 3 mL blue top tube
Pediatric: One 1.8 mL pediatric blud top tube
Pediatric: One 1.8 mL pediatric blud top tube
Minimum Volume
1 mL Plasma
Instructions
Tube must be filled to etched line to perform testing.
Samples must be centrifuged at 3000 rpm for 10 minutes or using a high-speed centrifuge. Platelet poor plasma should be separated into 1 ml aliquots. Samples should be frozen within one hour (best practice), however samples stable for 4 hours. Samples must remain frozen during transport. Any samples that are received thawed are not suitable for testing.
Samples must be centrifuged at 3000 rpm for 10 minutes or using a high-speed centrifuge. Platelet poor plasma should be separated into 1 ml aliquots. Samples should be frozen within one hour (best practice), however samples stable for 4 hours. Samples must remain frozen during transport. Any samples that are received thawed are not suitable for testing.
Specimen Stability
Ambient: 4 hours if cap has not been removed or punctured
Frozen: 6 months (-70C)
Frozen: 6 months (-70C)
Reject Criteria (Eg, hemolysis? Lipemia? Thaw/Other?)
Clotted specimen, underfilled tube, or gross hemolysis.
Methodology
Latex particle enhanced immunoassay on ACL TOP
Setup Schedule
Monday-Friday
Reference Range
55-200%
Clinical Significance
Blood group O individuals may have lower VWF activity levels than other ABO groups. Normal group O individuals may have VWF activity levels as low as 40-50%.
Performing Laboratory
West Virginia University Hospital, Inc.
