Preliminary observations on the technique of monitoring platelet aggregation in whole blood using a rotor system.

PLATELET aggregation is now recognised as an important early event in thrombosis. Problems associated with the measurement of the degree of platelet aggregation in plasma are outlined.An approach to the determination of the degree of platelet aggregation in whole blood using a new apparatus is described. When whole blood is placed in a circular transparent rotor chamber and subjected to rotational centrifugation at appropriate gravity forces the red cells are spun outwards leaving an inner zone of plasma containing single platelets. Since platelet aggregation does not occur in the absence of blood movement, the blood in the rotor is first agitated by discontinuous rotation using a suitable rotor drive system. Any platelet clumps which form are larger than single platelets and they may be later centrifuged out of the light path with the red cells. The clumps of platelets which have been removed from the plasma zone can be determined, by inference, by monitoring the plasma zone with a light beam. The precision in detecting platelet numbers may be improved by attention to factors such as the light path and wavelength.Because platelet concentrations, and perhaps plasma absorbance, vary in different individuals the light attenuation for blood plasma with and without platelets should be determined prior to estimating the degree of platelet aggregation under test conditions.