Click here for more information about laboratory operations and procedures
If you have additional questions regarding this test, please call: 415-353-1667
von Willebrand Factor - Factor 8 Binding Ratio
|Clinical Questions||Does my patient have von Willebrand disease? If so, which type?|
|Test group||von Willebrand|
|Patient Preparation||Patient should not have received plasma, cryoprecipitate, recombinant vWF or vWF concentrates prior to testing.|
|Collection Instructions||1. Check the expiration date on the label of the blue top vacutainer before drawing the patient.
2. For blood collection in a sodium citrate blue top, the tube must be filled to above the Minimum Fill Indicator on the tube. It is crucial to wait and allow the tube to stop filling before removing it from the needle.
3. With use of a butterfly needle, draw about 1 cc using a separate blue top to remove air from tubing, discard the first tube and then draw a second blue top tube filled to the full extent of the vacuum.
4. Tubes should not be filled past the Maximum Fill dashed line by either using a syringe or removing the tube cap.
|Container type||Blue top filled to full extent of vacuum|
|Amount to Collect||2.7 mL blood|
|Sample type||Citrated plasma|
|Preferred volume||1 mL plasma|
|Min. Volume||0.5 mL plasma|
|UCSF Rejection Criteria||Samples collected in outdated blue top vacutainer. Over-filled or under-filled tubes may be rejected|
|Processing notes||Freeze plasma in 0.5 mL aliquots. Order Quest #70068|
|Ref Lab Rejection Criteria||Sample received thawed, or after improper handling / storage|
|Synonyms||vwd; vWF-Factor VIII binding ratio; von Willebrand Disease type 2N; Factor VIII-von Willebrand Factor Binding Assay|
|Stability||Frozen at -20C 21 days|
|Turn around times||Set up at least 1x per month. Turnaround 2-3 weeks|
|Additional information||This test is used to differentiate between hemophilia A, hemophilia A carrier state, and type 2N vWD.
Type 2N-von Willebrand disease is an inherited bleeding disorder characterized by a qualitative defect in VWF in which it does not bind Factor VIII adequately, and the plasma half life of Factor VIII activity is shortened. Laboratory studies in patients with 2N VWD reveal a discrepancy between Factor VIII activity and von Willebrand factor antigen. Factor VIII activity levels are disproportionately depressed compared to VWF levels.
For selection of proper therapy, it is important to distinguish between 2N VWD and hemophilic disorders.
|Last Updated||3/24/2012 1:54:26 PM|