COMPLIANCE WITH ANTIPLATELET THERAPY IN PATIENTS WITH ISCHEMIC CEREBROVASCULAR-DISEASE - ASSESSMENT BY PLATELET-AGGREGATION TESTING

Background and Purpose Antiplatelet therapy is currently one of the me thods for preventing transient ischemic attacks and cerebral thrombosi s. Because antiplatelet agents are generally administered on a long-te rm basis, patient compliance is an important factor. The purpose of th is study was to determine the compliance of patients during antiplatel et therapy by testing platelet aggregation. Methods To establish the c onditions for measuring platelet aggregation, the platelet aggregation test was performed in patients taking 81 mg/d aspirin or 200 mg/d tic lopidine at the following final concentrations of aggregation-inducing agents: 0.5, 1, 2, and 4 mu mol/L ADP and 0.5 and 2 mu g/mL collagen. The optimum measurement conditions for assessing patient compliance w ere determined. Under the conditions determined in the first study, pl atelet aggregation was assessed, and the effects of treatment were stu died in 159 outpatients and 79 inpatients undergoing antiptatelet ther apy. If the antiplatelet effect was insufficient, compliance was check ed by interview. Results The agents used and the final concentrations found to be optimum for assessing platelet aggregation were 2 mu g/mL collagen for patients taking aspirin 81 mg/day and 2 mu mol/L ADP for patients taking ticlopidine 200 mg/d. In 17 (10%) of the 159 outpatien ts, platelet aggregation was not adequately reduced because of noncomp liance with their antiplatelet therapy. Conclusions This study indicat ed that monitoring of compliance is important for outpatients on antip latelet therapy. It is best if platelet aggregation can be checked, bu t when this is impossible it is necessary to assess compliance periodi cally and provide patient guidance.