Association of Recurrent Cerebral Infarction With Adenosine Diphosphate– and Collagen-Induced Platelet Aggregation in Patients Treated With Ticlopidine and/or Aspirin

Although the platelet aggregation test is the most common method for evaluating response to antiplatelet therapy, little is known about the association of recurrent cerebral infarction with platelet aggregation in the presence of various different antiplatelet drugs. We prospectively evaluated adenosine diphosphate (ADP)- and collagen-induced platelet aggregation and followed the incidence of recurrent infarction in patients categorized into 3 groups based on treatment; aspirin (n = 144), ticlopidine (n = 100), and aspirin + ticlopidine (n = 96). The patients in each treatment group were stratified into quartiles according to platelet aggregation, and the association of recurrent infarction with platelet aggregation was investigated. ADP-induced platelet aggregation values were significantly lower in the ticlopidine group and the aspirin + ticlopidine group compared with the aspirin group (P < .001), and collagen-induced platelet aggregation values were significantly lower in the aspirin group and the aspirin + ticlopidine group compared with the ticlopidine group (P < .001). In the aspirin group, the recurrence rate was somewhat higher in the higher aggregation quartiles than in the lower aggregation quartiles of 2 μg/mL collagen, the differences were not statistically significantly (P = .243). In the ticlopidine group, the recurrence rate was significantly higher in the lower aggregation quartiles compared with the higher aggregation quartiles of 1 μmol/L ADP (P = .025). No tendencies were found in the aspirin + ticlopidine group. Although the study is limited by its small sample size, the results suggest a possible difference between aspirin therapy and ticlopidine therapy in the pattern of association of recurrent infarction with platelet aggregation.