Monitoring of erythropoiesis by the serum transferrin receptor and erythropoietin.

Virtually all cells have transferrin receptors (a transmembrane glycoprotein) on their surface but in a normal adult, 80% of them are in the erythroid marrow. Some of them are lost into the circulation where they can be measured by immuno-assays. A direct and highly significant correlation exists between serum transferrin receptor level and erythron transferrin uptake in humans. The measurement of serum transferrin receptor has wide clinical applications for the quantitation of erythropoiesis. It can be used to study erythropoiesis in situations in which ferrokinetics is not acceptable such as pregnancy. It is particularly useful for serial studies, e.i., for monitoring the recovery of erythropoiesis after stem cell transplantation or after treatment with erythropoietin. Combined with the determination of serum erythropoietin, both evaluated in relation to the degree of anemia, they provide a physiological approach to the diagnosis of anemia. Thus, the simultaneous determination of hematocrit, reticulocytes, serum transferrin receptor and serum erythropoietin has high discriminatory value in distinguishing between a defect in erythroid proliferation, maturation or red cell survival. It is also particularly useful for detecting the presence of multiple mechanisms of anemia in the same patient.