'Spontaneous' platelet aggregation: its characteristics and relation to aggregation by other agents.

ABSTRACT

Platelet aggregation results of 117 patients were analysed. All had documented evidence of stroke, recurrent transient ischemic attacks and other neurologic symptoms, and all were hospitalized in the same Rehabilitation Center. Attention was specifically directed to the 'spontaneous' platelet aggregation (SPA) phenomenon, in terms of its characteristics and relationship to platelet count and aggregation induced by 3 physiologic agents. About 50% of the samples showed SPA but not all of them were hyperaggregable by other aggregating agents. A great deal of variation was found in the aggregation time, slope and extent of SPA. These variations do not always appear to relate to platelet count, or the responsiveness of platelets to other aggregating agents.