Rapid assay for von Willebrand factor activity using formalin-fixed platelets and microtitration technic

An inexpensive assay for von Willebrand factor using microtitration plates, formalin-fixed platelets, and ristocetin is described. With this technic, the assay for von Willebrand factor is simple enough to be considered for use in any diagnostic laboratory for patients with prolonged bleeding times.