von Willebrand Factor (vWF) Activity
Also known as: Ristocetin Cofactor
Use
Screen and diagnose von Willebrand factor (vWF) deficiency6,8-10
Special Instructions
If the patient's hematocrit exceeds 55%, the volume of citrate in the collection tube must be adjusted according to the Coagulation Collection Procedures.
Limitations
Patient samples may contain heterophile antibodies, such as human anti-mouse antibodies or rheumatoid factors, which might interfere with antibody assays, possibly giving a falsely elevated or reduced vWF result. Although a blocking reagent is used to minimize this interference, it cannot be completely eliminated. Therefore, diagnosing or ruling out any type of von Willebrand Disease should not solely rely on the result of the INNOVANCE® VWF Activity assay.
Methodology
Immunoassay
Biomarkers
LOINC Codes
- 107372-5
- 107372-5
Result Turnaround Time
1-3 days
Related Documents
For more information, please review the documents below
Specimen
Plasma
Volume
1 mL
Minimum Volume
Not provided
Container
Blue-top (sodium citrate) tube
Collection Instructions
Blood should be collected in a blue-top tube containing 3.2% buffered sodium citrate. Evacuated collection tubes must be filled to completion for proper blood-to-anticoagulant ratio. Mix by gentle inversion at least six times to ensure adequate mixing. Use a discard tube when employing a winged collection system.
Patient Preparation
Avoid warfarin for two weeks and heparin for two days prior to the test. Avoid drawing from an arm with a heparin lock or catheter.
Storage Instructions
Freeze.
Causes for Rejection
Gross hemolysis; clotted specimen; thawed in transit; improper labeling
Stability Requirements
| Temperature | Period |
|---|---|
| Frozen | 28 days |