Evaluation of an automated von Willebrand factor GPIbM activity assay compared to three alternative von Willebrand factor activity assays.

To overcome deficiencies of the traditional von Willebrand factor (VWF) ristocetin cofactor activity assay (VWF:RCo), several automated assays for VWF platelet-binding activity have been developed. Information on the performance of these assays and their diagnostic utility remains limited.