VWF Activity by Ristocetin Cofactor
|Profile or Test Panel||
Bleeding Diathesis with a Normal aPTT/PT Profile
If the aPTT is prolonged and the factor VIII is normal, this panel reflexes to an aPTT Reflexive Evaluation Profile.
|Indications||Requires VW Antigen and FVIII levels to interpret results|
|Test Information||Ristocetin is a negatively charged antibiotic that induces platelet agglutination in vitro. Plasma vWF activity is determined by the ability of patient’s plasma to support ristocetin-induced agglutination of normal formalin-fixed platelets. Reduced levels are characteristic of von Willebrand disease. Elevated values may occur with stress, inflammation, pregnancy, estrogen therapy, or exercise.|
|Additional Test Information||Normal ranges are included on testing report and can be made available upon request.|
|Sample Requirements||Whole Blood: 3.2% sodium citrated (blue top) OR
|Requested Volume||Two 5 ml 3.2% sodium citrated (blue top) tubes as whole blood OR
frozen plasma in 4 X 1mL aliquots in plastic tubes.
|Sample Information||Whole blood is preferred for testing, but if it is not possible to send whole blood tubes TO ARRIVE HERE WITHIN 2 HOURS of collection, then send frozen plasma. To prepare plasma, centrifuge blue top tubes at 1500g for 15 minutes and remove the plasma and centrifuge a second time at 1500g for an additional 15 minutes. Aliquot approximately 1 ml of plasma into 4 plastic tubes, and freeze.|
|Shipping Information||Whole Blood: Send at ambient temperature (18-25°C) and must be received within the lab in less than or equal to 2 hours after collection.
Frozen Plasma: Send on dry ice
Send samples to:
For additional information, please see Ordering Information
|Requisition Form||RFT- Hemostasis Reference Laboratory|
|Turn around Time (analytic time)||3 Business Days|
|Report/Results||Fax number required to receive report|