Ristocetin Cofactor

Must be collected only at the following locations:
Duke Street Lab Testing
Suburban Pavilion Lab Testing
Women and Babies' Hospital Lab Testing

4459

RISTO
LAB3020606

1 mL frozen platelet-poor plasma collected in a 3.2% sodium citrate (light blue-top) tube

0.5 mL

Platelet poor plasma: Centrifuge light blue-top tube for 15 minutes at approximately 1500 g within 60 minutes of collection. Using a plastic pipette, remove plasma, taking care to avoid the WBC/platelet buffy layer and place into a plastic vial. Centrifuge a second time and transfer platelet-poor plasma into a new plastic vial. Plasma must be free of platelets (<10,000/mcL). Freeze immediately and ship on dry ice.

Note: Storage of whole blood at refrigerated temperatures prior to processing may lead to cryoprecipitate formation and falsely low Factor VIII and von Willebrand Factor studies.

Frozen

Room temperature: Unacceptable
Refrigerated: Unacceptable
Frozen: 30 days

Thawed plasma • Received at room temperature or refrigerated • Hemolysis • Lipemia

Set up: Mon-Fri; Report available: 2-5 days

42-200 % normal

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.