Ristocetin-induced patient platelet aggregation. (A) Aggregation of patient's PRP by 0.5 mg/mL ristocetin before (1) and after daily intake of 1,000 mg aspirin for 7 weeks (2). (B) Intensity of aggregation response as a function of ristocetin concentration during aggregation of normal (○) and patient (•) PRP, 7 weeks after daily intake of 1,000 mg aspirin.