von Willebrand Factor Assay

von Willebrand Factor Assay

🔬Introduction Example:

The von Willebrand Factor Assay, also known as the Ristocetin Cofactor Test, is a specialized coagulation test used to evaluate platelet function and assist in diagnosing von Willebrand’s disease (vWD).

Synonyms: Ristocetin Cofactor, vW Factor Assay

🧪Specimen: Plasma

🧪Container: Blue top (sodium citrate) tube

Collection: A sample will be collected by a clinic or lab technologist.

🧊Storage Instructions: To send frozen, immediately separate into plastic vials.

⚠️Reason to Reject Sample:

Samples that were received more than two hours after collection were hemolyzed, clotted, and the tube wasn’t full.

ℹ️Special Instructions: Make an appointment with the lab in advance.

📊Reference Range:

Interpretation of platelet aggregation patterns, normal plasma/ platelets aggregate when exposed to ristocetin.

🧬Use:

Aid in determining the difference between von Willebrand’s disease and hemophilia.

⚙️Methodology:

Modified platelet aggregation, measurement of agglutination of fresh washed or formalin-fixed platelets by patient’s plasma as compared to agglutination produced by a “standard plasma” used to prepare a standard curve, botrocetin snake venom based platelet agglutinating test.

ℹ️Additional Information:

A factor that causes platelet aggregation in response to ristocetin is absent from the plasma of patients with von Willebrand’s disease.

📚References

1. Bloom AL, “von Willebrand Factor: Clinical Features of Inherited and Acquired Disorders,” Mayo Clin Proc, 1991, 66(7):743-51.
2. Triplett DA, “Laboratory Diagnosis of von Willebrand’s Disease,” Mayo Clin Proc, 1991, 66(8):832-40.
3. Jacobs, Demott, Finley, Horvat, Kasten.JR, & Tilzer, “Laboratory Test Handbook” Lexi-Comp Inc, 1994, (216) 650-6506