von Willebrand Factor (vWF) Profile
Use
Diagnose von Willebrand factor (vWF) deficiency6,8-10
Special Instructions
If the patient's hematocrit exceeds 55%, adjust the citrate volume in the collection tube accordingly. Refer to Coagulation Collection Procedures for detailed instructions. Ensure blood is collected using the proper technique to avoid hemolysis or clotting, which can affect test results.
Limitations
Transient clinical conditions can cause temporary increases in vWF levels, such as stress, inflammation, acute infection, physical exercise, and surgery. Hormonal changes, including estrogen administration, can also increase vWF levels. During pregnancy, vWF levels are typically elevated two- to threefold, especially in the later trimesters. Patients with type O blood usually present lower vWF levels (about 30% less) compared to other blood types. Such variabilities can complicate diagnosis, requiring careful interpretation of results.
Methodology
Other
Biomarkers
LOINC Codes
- 48593-8
- 107372-5
- 3209-4
- 27816-8
Result Turnaround Time
2-3 days
Related Documents
For more information, please review the documents below
Specimen
Plasma
Volume
2 mL
Minimum Volume
Not provided
Container
Blue-top (sodium citrate) tube
Collection Instructions
Citrated plasma samples should be collected by double centrifugation. Draw blood into a blue-top tube containing 3.2% buffered sodium citrate, ensuring the tube is filled to completion for a correct blood-to-anticoagulant ratio. Immediately mix the sample by gentle inversion at least six times to properly combine anticoagulant with blood. Use a discard tube if drawing with a winged blood collection device, then centrifuge and carefully separate the plasma for transport.
Patient Preparation
Patients should be calm before blood draw to prevent elevation of vWF levels due to stress. Avoid drawing from an arm with a heparin lock or heparinized catheter. Certain anticoagulant therapies may interfere with Factor VIII activity results.
Storage Instructions
Freeze immediately and maintain frozen until tested.
Causes for Rejection
Gross hemolysis; clotted specimen; frozen specimen thawed in transit; improper labeling; improper collection tube