Dissociation between factor VIII (activity and antigen) and ristocetin-induced platelet aggregation in von Willebrand's disease.

Previously we showed that von Willebrand patients could be separated into 2 groups on the basis of ristocetin-induced platelet aggregation and factor VII (antigen and activity). Ristocetin-induced platelet aggregation and factor VIII exhibited a positive correlation. This paper deals with 5 out of 31 examined von Willebrand patients in which ristocetin-induced platelet aggregation was not in correlation either with factor VIII activity or antigen. The importance of these findings is discussed.