Characterization of the normoblast population in beta-thalassaemic blood by rapid-flow cytofluorometry

Samples of peripheral blood from patients with beta-thalassaemia major which contained significant numbers of nucleated normoblasts were stained with acridine orange and analyzed with rapid-flow cytofluorometry. The pyknotic normoblast-nuclei gave less green 'DNA' fluorescence than the (diploid) leucocytes and constituted a separate, distinct subpopulation. Mean values of the fluorescence intensities and standard deviations as displayed by multichannel analyses gave a numerical value for normoblasts with regard to their maturation stages. These mean values correlated with the differential counts of 'early and late' normoblasts in the light microscope under rigidly standardized conditions. Rapid-flow cytofluorometry thus provides an objective and quantitative way to monitor and define peripheral blood normoblast populations as a measure of the severity of 'erythropoietic stress'.