A newly available dried concentrate of antihemophilic factor (Profilate®, Abbott Laboratories) was compared with standard, blood-bank prepared cryoprecipitate In the control of bleeding in a patient with von Willebrand's disease. Profilate effectively raised plasma levels of factor VIII but produced only half the expected increase in plasma ristocetin aggregation factor (RAF), and this RAF did not bind readily to the platelets in the presence of ristocetin. Furthermore, the Profilate had little effect upon the bleeding time or the clinical hemorrhage. In contrast, the cryoprecipitate did increase plasma RAF to the expected level, and this RAF bound readily to the patient's platelets in the presence of ristocetin. Cryoprecipitate promptly controlled bleeding. We conclude that the RAF present in Profilate retains in vitro activity but is incapable of augmenting platelet function in vivo.
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