Abstract

A modification of Salzman's method has been used in an attempt to provide an assay in vitro for the von Willebrand factor. Platelet adhesiveness was increased in von Willebrand's disease by previously coating the beads with normal or haemophilic plasma or cryoprecipitate, whereas von Willebrand plasma had no corrective effect. Antihaemophilic factor (AHF) concentrates were studied in the same way and results compared with experiments in vivo.