Test Overview
Platelet agglutination using washed platelets in the presence of ristocetin.
Aid with the diagnosis of von Willebrand disease.
50 - 150%
* Reference ranges may change over time. Please refer to the original patient report when evaluating results.
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
1 hour
- Coagulation Ristocetin Co-Factor Activity
- Ristocetin Co-Factor Activity
- VWF
- RISTOCETIN COFACTOR ASSAY
Specimen Requirements
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.
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.