Iron deficiency and erythropoiesis: new diagnostic approaches.

Iron deficiency anemia is one of the most common diseases worldwide. In the majority of cases, the presence of hypochromic microcytic anemia and biochemical evidence for depletion of body iron stores makes the diagnosis relatively straightforward. However, in several clinical conditions, classic biochemical indices such as serum iron, transferrin saturation, and ferritin may not be informative or may not change rapidly enough to reflect transient iron-deficient states (functional iron deficiency), such as the ones that develop during recombinant human erythropoietin (r-HuEPO) therapy. The identification and treatment of iron deficiency in settings such as r-HuEPO therapy, anemia of chronic disease, and iron deficiency of early childhood may be improved by the use of red cell and reticulocyte cellular indices, which reflect in almost real time the development of iron deficiency and the response to iron therapy. In the anemia of chronic disease, measurements of plasma cytokines and iron metabolism regulators such as hepcidin (when available) may be helpful in the characterization of the pathophysiologic basis of this condition. The ratio of serum transferrin receptor (sTfR) to serum ferritin (R/F ratio) has been shown to have excellent performance in estimating body iron stores, but it cannot be used widely because of the lack of standardization for sTfR assays. The combination of hematologic markers such as reticulocyte hemoglobin content, which decreases with iron deficiency, and R/F ratio may allow for a more precise classification of anemias.