Comparison between induced platelet aggregation and circulating platelet aggregates as platelet function tests in patients with transient ischemic attacks.

Routine blood analysis, platelet counts, number of circulating platelet aggregates (CPA) and platelet aggregation in vitro against adenosine-diphosphate (ADP), epinephrine and collagene were studied in 45 healthy controls, in 10 hospitalized patients with other neurological diseases than stroke and in 12 patients with transient ischemic attacks (TIA) before and after prophylactive treatment with anticoagulants (AC) or antiplatelet drugs (APD). Except for lower hemoglobin and hematocrit levels in women, sex, smoking, oral contraceptives of pregnancy did not significantly influence the routine blood parameter. Smoking females taking oral contraceptive had an increased number of CPA and the most easily induced aggregation in vitro. Patients with TIA had no significant differences in blood or platelet findings versus the healthy controls (except smoking females on oral contraceptives) or the non-stroke patients, even though individual patients could have high numbers of CPA and an easily induced platelet aggregation in vitro. Treatment with AC did not influence platelet function, whereas APD therapy decreased the number of CPA and inhibited the secondary platelet aggregation in vitro.