Test Overview
Test Methodology

Platelet agglutination using washed platelets in the presence of ristocetin.

Test Usage

Aid with the diagnosis of von Willebrand disease.

Reference Range *

50 - 150%

* Reference ranges may change over time. Please refer to the original patient report when evaluating results.

Test Limitations

vWF disease necessitates a series of clinical and laboratory evaluations including patient and family history, vWF activity, factor VIII activity, and von Willebrand factor antigen.

Test Details
Days Set Up
Friday
Analytic Time

1 hour

Soft Order Code
VWF
MiChart Code
Von Willebrand Antigen
Synonyms
  • Coagulation Ristocetin Co-Factor Activity
  • Ristocetin Co-Factor Activity
  • VWF
  • RISTOCETIN COFACTOR ASSAY
Laboratory
Hematopathology
Section
Coagulation
Specimen Requirements
Collection Instructions

Collect specimen in a blue top (citrate 3.2%) tube. Mix by inversion. Specimen should arrive at lab within 3 hours of collection; transport at room temperature. Alternatively, centrifuge, aliquot plasma into a plastic vial, and freeze the specimen within 4 hours of collection. Transport frozen specimen on dry ice. Collection of the blood through lines that have been previously flushed with heparin should be avoided. If the blood must be drawn through a VAD (vascular access device), the line should be flushed with 5 mL of saline and the first 5 mL of blood or six dead space volumes of the VAD discarded.

Rejection Criteria
Specimens will be rejected if not properly filled, clotted, grossly hemolyzed, or contaminated with heparin.
Blue Top Tube
Normal Volume
Full 2.7mL tube or 1mL plasma aliquot
Minimum Volume
Full 1.8mL tube or 1mL plasma aliquot
Storage Temperature
Room temperature for whole blood or frozen aliquot of citrated plasma
Additional Information

VWF is an acute phase reactant. Elevated levels are seen during pregnancy, estrogen therapy, inflammation, acute infection, post surgery, physical exercise, or a stressful situation. Individuals with type O blood group have lower levels of vWF compared to other blood groups.

Billing
CPT Code
85245
Fee Code
31118
LOINC
6014-5
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