Laboratory diagnosis of iron deficiency: IRON DEFICIENCY ASSESSMENT

Abstract

SUMMARY Worldwide, iron deficiency (ID) is the leading risk factor for disability and mortality, affecting both developing and developed countries with major consequences for human health as well as social and economic development. ID results from any situation in which dietary iron intake does not balance iron demands because of increased iron requirements, limited external supply and/or increased blood loss. In absolute ID, ferritin stores are progressively diminished; the supply of iron to transferrin is compromised, and as a consequence transferrin saturation is decreased. In functional ID (FID), iron stores cannot be mobilized as fast as necessary from the repleted macrophages of the reticuloendothelial system to the bone marrow. This condition is typical of the anemia of chronic diseases (ACD) because of inflammation-induced increased hepcidin levels. Both absolute and functional ID may evolve to ID anemia (IDA). The diagnosis of ACD + IDA remains challenging. In addition to a soluble transferrin receptor (sTfR)/log ferritin ratio > 2, there are several important hematological indices that may help in the diagnosis of absolute ID in ACD, such as the reticulocyte hemoglobin content and the percentage of hypochromic red blood cells. In this paper we review the causes of ID, the different laboratory tests available and how to combine them to establish a correct diagnosis of ID, FID, IDA, ACD and ACD + IDA.