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Labcorp Oklahoma, Inc.
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Von Willebrand Factor Activity (Ristocetin Cofactor)

Order Name RISTOC COF
Test Number: 1502200
Revision Date 10/08/2024
Test Name Methodology LOINC Code
Von Willebrand Factor Activity (Ristocetin Cofactor)
Clot Detection 6014-5 
SPECIMEN REQUIREMENTS
Specimen Specimen Volume (min) Specimen Type Specimen Container Transport Environment
Preferred 2 mL (1) Plasma Sodium Citrate 3.2% (Blue Top) Frozen
Instructions Frozen Citrated plasma, plasma must be double spun and frozen in 1.5 ml aliquots. Do not pool plasma from multiple tubes! Do not thaw. Hemolyzed specimens are not acceptable. See Specimen Collection Section, Coagulation Testing. Fasting for at least 8 hours is preferred.

Specimen Stability: Room temperature: unacceptable, Refrigerated: unacceptable, Frozen: 3 months
GENERAL INFORMATION
Testing Schedule Wed 
Expected TAT 1-7 Days  
Clinical Use Also known as von Willebrand Factor Activity 
CPT Code(s) 85245
Lab Section Coagulation