Which statement about ristocetin cofactor testing in von Willebrand disease is true?

Which statement about ristocetin cofactor testing in von Willebrand disease is true?

• A. It is normal in all cases
• B. It is significantly decreased
• C. It is not affected by ristocetin
• D. It is decreased

Answer: (D)

Ristocetin cofactor activity reflects how well von Willebrand factor can support ristocetin-induced platelet aggregation by binding to the platelet GPIb receptor. In von Willebrand disease, there is either a quantitative deficiency or a qualitative defect of VWF, so its ability to mediate this interaction is reduced. That leads to a decreased VWF ristocetin cofactor activity. The degree of decrease can vary with the VWD type and severity, so it’s not necessarily a uniform “significant” decrease in every case, but it is consistently reduced overall. It is not normal in all cases and the test relies on ristocetin to reveal the VWF-platelet interaction.

Ristocetin cofactor activity reflects how well von Willebrand factor can support ristocetin-induced platelet aggregation by binding to the platelet GPIb receptor. In von Willebrand disease, there is either a quantitative deficiency or a qualitative defect of VWF, so its ability to mediate this interaction is reduced. That leads to a decreased VWF ristocetin cofactor activity. The degree of decrease can vary with the VWD type and severity, so it’s not necessarily a uniform “significant” decrease in every case, but it is consistently reduced overall. It is not normal in all cases and the test relies on ristocetin to reveal the VWF-platelet interaction.