Regulation of Erythropoiesis . I . Erythropoietin Assay

By WARD D. N0YE5, BILL M. DO st AND LoRErrA C. Wails T HE RATE of red cell production is regulated by a plasma factor( s ) termed erythropoietin. While injection of exogenous plasma rich in this substance (or substances ) has been shown to induce an increase in the total circulating red cell mass by stimulation of erythropoiesis,13 quantitation of erythropoietin has been hampered by lack of specific chemical methods. Numerous biological assays have been developed, each capable of demonstrating the presence of potent erythropoietin, but varying in sensitivity and reliability.4 With the increasing availability of these assays in clinical diagnosis comes the necessity of interpreting the results in the light of the patient’s disease. The purpose of this paper is to examine the meaning of an erythropoietin assay using radioiron utilization in polycythemic rats, and to interpret the results obtained from patients with refractory anemia and with polycythemia.