Special Instrumentation in the Ocular, Neurological and Hematology Laboratories: Examination of the Dynamics of Platelet Aggregation and Disaggregation Using Computerized Image Analysis

Thromboembolic disease is a major cause of death in the United States today. Because platelet aggregation plays an important role in thrombus formation, many attempts have been made to study it in vitro. The dynamics of platelet aggregation and disaggregation are of especial interest but are presently not well understood because the most commonly used method of study (light transmission aggregometry) is inadequate. Using the TEXAC whole picture image analyzer, a quantitative method has been developed for measuring platelet aggregation which provides a complete distribution of platelet aggregate sizes. Development of this new method called Computerized Platelet Aggregation Analysis (C.P.A.A.) required multi-stage removal of background noise, image enhancement of low contrast unstained particles (platelets), and derivation of a correction factor for chance adjacency of platelets. Platelets from four healthy volunteers were studied to determine the degree of aggregation and disaggregation Poor to and after chemical and physical platelet stimulation with a spin bar. C.P.A.A. was able to recognize platelet aggregates which were ignored by light transmission aggregometry. The capacity to quantify platelet aggregate size distributions of varied etiology and to follow the dynamics of platelet aggregation and disaggregation is a prerequisite to the rational analysis of both normal and abnormal hemostasis and thrombosis.