[Erythropoietin determination in clinical medicine]

Erythropoietin (EPO) is a prime stimulating factor for red cell production. EPO is a glycoprotein which has a molecular weight of 34,000, and is mainly produced by the kidney. EPO stimulates the differentiation and proliferation of erythroid progenitor cells in the bone marrow. The rate of production of EPO is regulated primarily by renal oxygen availability. Because anemia reduces renal oxygen availability, anemic stress accelerates EPO production in the kidney. Recently, EPO has mainly been determined by radioimmunoassay. Serum EPO titer is usually inversely correlated with hemoglobin concentration, as typically shown in iron deficiency anemia. Serum EPO titers in aplastic anemia are much higher than those in iron deficiency anemia relative to the hemoglobin concentration. Serum EPO titers in anemia caused by malignancies sometimes differ considerably among patients. Serum EPO in renal anemia usually show low titers irrespective of the degree of anemia. Serum EPO titers in untreated polycythemia vera are lower than those in treated polycythemia vera or secondary polycythemia. Determination of serum EPO is useful in differential diagnosis of polycythemia vera. Recombinant human EPO has been used to treat various anemias including renal anemia, refractory anemia, anemia in malignancies and secondary anemia. Determination of serum EPO titers is also valuable in many other situations of clinical medicine.