Serum immunoreactive erythropoietin in health and disease

The currently available radioimmunoassay for erythropoietin (Epo) using recombinant reagents is an accurate, reproducible, sensitive and specific assay which can be used to identify whether lack of Epo is contributing to anemia and, by extension, whether therapy with recombinant Epo might be appropriate. Elevation of the serum Epo level with anemia suggests that a marrow abnormality is the cause of the anemia, while a “high” Epo level in a non‐anemic or plethoric patient suggests the presence of hypoxia or autonomous Epo production. Liver disease can elevate the serum Epo level, while modest degrees of anemia do not affect it appreciably. The lowest Epo levels occur in polycythemia vera, but in a particular patient this finding is not completely diagnostic.