The diagnostic plot: a concept for identifying different states of iron deficiency and monitoring the response to epoetin therapy.

Iron balance is regulated by the rate of erythropoiesis and the size of the iron stores. Anemia that accompanies infection, inflammation, and cancer (anemia of chronic disease) features normal or increased iron stores, although patients may have functional iron deficiency, namely, an imbalance between iron requirements of the erythroid marrow and the actual supply. The proportion of hypochromic red cells and the hemoglobin content of reticulocytes are direct indicators of functional iron deficiency. Biochemical markers, especially the soluble transferrin receptor/log ferritin ratio (ferritin index), are useful indicators of the iron supply to erythropoiesis. The relationship between functio…