Abstract :
The hemoglobin concentration and the hematocrit percentage are usually used to diagnose anemias and erythrocytoses and to monitor their treatment and progress. However, they may be misleading because of dehydration or dilution and it is imperative to keep in mind their relationship to the size of the red-cell mass. This size is determined by the cellular kinetics of four distinct compartments which make up the erythron: the stem cells, the progenitor cells, the precursor cells and the mature cells. Under normal physiologic conditions, the kinetics of the progenitor-cell compartment determines the size of the red-cell mass but, under abnormal conditions, the kinetics of each of the compartments may affect the size. In this review, normal and abnormal kinetics of the four compartments are defined and related to the size of the red-cell mass and the pathogenesis of anemias and erythrocytoses.
