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Ristocetin Cofactor : 4459
MessageThe aliquot must remain frozen. Freeze thaw cycle will adversely affect specimen integrity. CRITICAL FROZEN: Separate specimens must be submitted when multiple tests are ordered.
Test Code
RISTO or 4459
Alias/See Also
RcoF,von Willebrand Factor Activity
CPT Codes
85245
Instructions
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.
Transport Container
Preferred Specimen
1 mL frozen platelet-poor plasma collected in 3.2% sodium citrate (light blue-top) tube
Minimum Volume
0.5 mL
1 mL frozen platelet-poor plasma collected in 3.2% sodium citrate (light blue-top) tube
Minimum Volume
0.5 mL
Transport Temperature
Frozen.
Specimen Stability
Room temperature: Unacceptable; Refrigerated: Unacceptable; Frozen: 30 days
Reject Criteria (Eg, hemolysis? Lipemia? Thaw/Other?)
Hemolysis; Lipemia; Thawed plasma received room temperature or refrigerated
Methodology
Platelet Agglutination
Setup Schedule
Monday, Wednesday, Friday
Report Available
1-4 daya
Reference Range
42-200% normal
Clinical Significance
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.
Performing Laboratory
med fusion
