Platelet volume heterogeneity in acute thrombocytopenia

Platelet volume and count were measured by aperture impedance techniques in rats during acute thrombocytopenia 2, 6, 12 and 24 h and 3, 6, 9 and 11 days after a single injection of anti-platelet serum (APS). Platelet volume heterogeneity was quantified by four statistical parameters: the measure of central tendency, dispersion, asymmetry and convexity. None of the volume distributions, including the controls, was log Gaussian. Mean platelet volume increased for the first 6 h post APS and then started to decrease although the platelet count had not started to rise. There was an initial increase, followed by a smooth decrease to control values, in the coefficient of variation (suggesting an initial increased dispersion about the mean platelet volume) with concomitant decreases in asymmetry and convexity. In contrast the age of the platelets immediately after the APS injection must have a decreased dispersion about the mean age compared with control values. These facts are used to show that young platelets are not synonymous with large platelets even under the stress of acute thrombocytopenia and support the concept that thrombopoiesis is the dominant factor in determining platelet volume heterogeneity.