DETECTION OF PLATELET AGGREGATES WITH A PARTICLE COUNTING METHOD USING LIGHT-SCATTERING

A novel method to detect platelet aggregation by means of the particle counting technique using light scattering has been developed. An opti cal device designed to focus on a limited area of platelet-rich plasma measured the intensity of light scattered by particles passing throug h the area, minimizing multiple light scattering. The use of polystyre ne spheres of different diameters confirmed that the light scattering intensity increases in proportion to the particle size in a suspension . Platelet activation induced by various agonists resulted in light sc attering of higher intensities, which correlated well with the number and size of aggregates as observed under a microscope. These findings confirmed that the intensity of light scattering detected by the new d evice provides information on the number and size of aggregates in a s uspension. The new method was compared with conventional platelet aggr egometry using overall light scattering or changes in light transmissi on (optical density). The new device appeared to be particularly sensi tive to small aggregates such as those formed in platelet activation i nduced by low concentrations of agonists. Furthermore, the new method has an advantage over the conventional aggregometry, in that it allows the aggregate size distribution and the extent of aggregation to be e stimated. (C) 1994 Academic Press, Inc.