Ristocetin Cofactor Activity - Machaon Diagnostics

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Ristocetin Cofactor Activity

Justification

The Ristocetin Cofactor assay assess von Willebrand factor (VWF) function, measuring the ability of VWF to bind to platelet glycoprotein 1b. Ristocetin Cofactor Activity should be ordered as part of a von Willebrand Disease (VWD) workup. Decreases in Ristocetin Cofactor Activity are consistent with von Willebrand Disease. Additional testing, including but not limited to VWF Antigen, Factor VIII Activity, VWF Multimer, and VWD Complete genetic sequencing, is required for confirmation and subtyping of VWD.

STAT: < 24 hours (7 days a week)

Platelet Agglutination

Draw Tube: Blue Top

Sample Type: Citrated Plasma

Specimen Requirements

	Sample Type	Volume Required	Minimum Volume	Stability
PREFERRED	Citrated Plasma	1mL	0.5mL	Frozen (-20C): 2 weeks Frozen (-80C): 6 months
ALTERNATIVE	-	-	-	-

REJECTION CRITERIA	Thawed in transit, refrozen or clotted sample
SPECIAL INSTRUCTIONS	-

General Information

METHODOLOGY	Platelet Agglutination
STAT TAT	< 24 hours (7 days a week)
STAT TAT Performance	> 90% of results released in 24 hours 7 days a week
ROUTINE TAT	< 3 days (M-F)
ALTERNATIVE NAMES	von Willebrand Factor (VWF) activity, VWF:Rco, Rco
DESCRIPTION	The rate of Ristocetin-induced agglutination of a standardized platelet suspension is proportional to the concentration and functional activity of von Willebrand factor in the sample added.
LIMITATIONS	May be falsely low in individuals with certain polymorphisms in the vWF gene that affect binding of ristocetin to vWF.
NORMAL RANGE	50-150%
ASSOCIATED TESTING	-
REFERENCES	-
SAMPLE REPORT	Upon request
NEW YORK STATE APPROVED	-

Test Codes

ORDER CODE	P3118
CPT CODE	85245
LOINC CODE	6014-5