The effect of the platelet count on the aggregation response and adenosine triphosphate release in an impedance lumi-aggregometer.

Platelet aggregation studies are usually performed in either electrical impedance or optical systems and the release reaction assessed by quantitating adenosine triphosphate (ATP) from luminesence produced by the firefly luciferin-luciferase system. In evaluating the results of such studies, attention is paid to a variety of parameters such as the slope of the aggregation response and the maximum aggregation expressed as percent light transmission in optical and as Ohms in electrical impedance systems. Although threshold platelet counts are frequently cited below which the performance of these studies is technically difficult, the influence of the platelet count within the normal range on the results of such studies has not been prospectively addressed. This study examines the relationship between the aggregation response, ATP release and the platelet count in a lumi-impedance system. It is clear that the platelet count influences the results in this system and requires consideration in the interpretation if an erroneous conclusion is to be avoided.