Sensitivity of platelets to aspirin in von Willebrand's disease.

The sensitivity of collagen-induced platelet aggregation to aspirin was measured in vitro on platelet-rich plasma from 20 normal subjects and five patients with von Willebrand's disease. Although aspirin tolerance tests performed in vivo at the same time showed an abnormal prolongation of the bleeding time in three of the patients studied, no evidence was found for an enhanced sensitivity to aspirin in vitro.