RISTOCETIN COFACTOR ASSAY

Code
000.0000
Name
RISTOCETIN COFACTOR ASSAY
Category
None
Department
Send-Out
Start Date
Expiration Date
Synonyms
vonWillebrand Factor
CPT Codes
85245
Site
SBMF
Reference Test
25250
ATLAS Test Code

Specimen Information

Type

Light blue top (3.2% buffered sodium citrate) tube, Platelet-poor plasma (PPP)

Volume

2.0 mL (Two aliquots, 1.0 mL each)

Transport Info

Separate plasma from cells immediately
• Promptly centrifuge 15 minutes
• Carefully transfer plasma portion of sample to separate plastic tube using plastic pipette
• Centrifuge transferred plasma sample again to produce platelet-poor plasma (PPP)
• Use second plastic pipette to carefully transfer PPP sample into 2 plastic aliquot tubes
Frozen

Fasting Required?
False
Patient Instructions

Reference Range

60-160%
Critical Low Value: 30%
Critical High Value: 500%

Methodology

Spectrophotometry

Clinical Significance

Aid in the diagnosis of vonWillebrand Disease and of diseases with changes in the Ristocetin Cofactor activity, such as vascular endothelial lesions, inflammations, and preoperative screening of bleeding tendency.

Ristocetin cofactor (vW factor; VIII:vW; vonWillebrand factor) is the property of the Factor VIII protein that is responsible for the agglutination of platelets in the presence of ristocetin. Decreased quantities or abnormalities of the vonWillebrand factor are associated with vonWillebrand syndrome, thus making quantitation of the factor most valuable in the diagnosis and evaluation of this coagulopathy.Levels of vonWillebrand factor are determined by the ability of a test plasma and ristocetin to induce agglutination of a standardized platelet suspension.

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