What is ristocetin cofactor?
Ristocetin Cofactor – 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.
How does ristocetin cofactor assay work?
Ristocetin cofactor assay uses the patient’s platelet poor plasma (with vWF but no platelets) and adds ristocetin and exogenous formalin-fixed platelets which can passively agglutinate (but not actively aggregate, as they are dead).
At what age is von Willebrand disease diagnosed?
76% of men with VWD had been diagnosed by age 10, but 50% of women with VWD were not diagnosed until after age 12.
What if ristocetin cofactor is low?
If the VWF antigen test is normal or nearly normal and the VWF activity (Ristocetin Cofactor) is decreased, then the person may have Type 2 VWD. Further testing (e.g., VWF multimeric analysis) will be required to determine which subtype is present.
What kind of infection is ristocetin used for?
?) Ristocetin is an antibiotic, obtained from Amycolatopsis lurida, previously used to treat staphylococcal infections. It is no longer used clinically because it caused thrombocytopenia and platelet agglutination.
How does ristocetin affect platelets in the blood?
In an unknown fashion, the antibiotic ristocetin causes von Willebrand factor to bind the platelet receptor glycoprotein Ib (GpIb), so when ristocetin is added to normal blood, it causes agglutination of fixed platelets or initiates the initial agglutination phase of aggregation of live platelets.
When is the ristocetin cofactor assay is used?
Pseudo-vWD: hyperactive agglutination occurs (when the ristocetin cofactor assay is used, the agglutination is hypoactive) Bernard-Soulier syndrome: hypoactive agglutination occurs (when the ristocetin cofactor assay is used, the agglutination is normal)
Why does ristocetin increase the binding of vWD?
This increased binding causes vWD because the high-molecular weight multimers are removed from circulation in plasma since they remain attached to the patient’s platelets.
