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Ristocetin Cofactor (VWF)
MessageFasting for 8 hours is preferred.
Test Code
LAB2424
Quest Code
4459
Alias/See Also
VWF
CPT Codes
85245
Preferred Specimen
1 mL frozen platelet-poor plasma collected in a 3.2% sodium citrate (light blue-top) tube
Minimum Volume
0.5 mL
Instructions
Separate and freeze plasma ASAP.
Transport Container
Transport tube
Transport Temperature
Frozen
Specimen Stability
Room temperature: Unacceptable
Refrigerated: Unacceptable
Frozen: 30 days
Refrigerated: Unacceptable
Frozen: 30 days
Reject Criteria (Eg, hemolysis? Lipemia? Thaw/Other?)
Hemolysis; received room temperature or refrigerated; lipemia
Methodology
Platelet Agglutination
Setup Schedule
Wed, fri
Report Available
4-8 days
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
| Quest Diagnostics Nichols Institute-Chantilly VA |
| 14225 Newbrook Drive |
| Chantilly, VA 20151-2228 |
