THE PLATELET-AGGREGATION SCORE AND ITS CORRELATION TO BETA-THROMBOGLOBULIN AND PLATELET FACTOR-4 LEVELS

We describe a new method of interpreting platelet aggregometry results and its correlation to platelet secretory protein levels. We studied 123 healthy male volunteers, 37-85 years of age. The aggregation respo nse to 2.5 mu M ADP was measured in a standardized platelet suspension (SPS) prepared from platelet-rich plasma. Turbidimetric measurements included amplitude of the primary aggregation wave (Amp(1)), maximum a ggregation amplitude (A(max)), and area under the aggregation curve (S -agg). A platelet aggregation (PA) score was calculated as (A(mp1)/A(m ax)). S-agg.(whole-blood platelet count/SPS platelet count). beta-Thro mboglobulin (beta-TG) and platelet factor 4 (PF4) levels were measured by radioimmunoassay. The PA score correlated significantly (p < 0.000 1) with beta-TG (r = 0.86) and PF4 (r = 0.87). It was concluded that t he PA score correlates closely with individual subjects' propensities to platelet activation, as reflected by plasma beta-TG and PF4 levels.