Useful For: Von Willebrand Disease is the most common hereditary bleeding disorder. Von Willebrand Factor is necessary for platelet adhesion to injured endothelium. Ristocetin Cofactor is useful in assessing binding of von Willebrand Factor to platelet factor GP1b. When combined with other tests, results are useful in categorizing the type of von Willebrand Disease.
Methodology: Platelet Agglutination
Specimen Requirements: 1 blue-top (citrate) tube (minimum: the remaining platelet poor plasma separated from 2.7 mL whole blood/0.5 mL plasma). Draw following an overnight (8-10 hour) fast. Centrifuge (15 minutes) blue-top immediately. Submit in 2 aliquots, 1 mL each. Separate plasma and FREEZE immediately. Send specimen frozen in plastic vial.
If using a butterfly collection set, fill a 1 mL waste tube prior to blue-top. This ensures full blood volume in blue-top.
Tube must be filled to capacity.
Draw specimen by vacuum. Do not over-fill the tube.
Hemolyzed specimens are not acceptable.
Analytical Time: 3 days
Days Set Up: Monday through Friday