Iron Deficiency Anemia: Diagnosis

Laboratory testing is necessary to diagnose iron deficiency anemia. A complete blood count (CBC) reveals a low hematocrit and hemoglobin concentration and usually a decreased mean corpuscular volume. The red blood cell distribution width (RDW) is elevated. Iron deficiency is one of the most common causes of an elevated platelet count.

The current preferred means of diagnosis is a serum ferritin test, which reflects total body iron stores. Note, however, that ferritin is an acute–phase reactant that may be elevated in cases of inflammation, infection, malignancy, and liver disease, producing a false–negative result.

A blood smear may reveal hypochromic, microcytic red blood cells. However, such cells are also found in the context of other disorders, such as anemia of chronic disease and thalassemia.

Additional useful tests include transferrin (often measured indirectly as the total iron–binding capacity, which is elevated in iron deficiency) and serum iron, which is usually decreased. These tests are less reliable during acute illnesses or in patients with severe chronic diseases. Transferrin is also elevated in women who are pregnant or using oral contraception.

Bone marrow biopsy to determine marrow iron stores was a standard means of diagnosis in the past, but now is only rarely necessary to diagnose iron deficiency anemia.

An interesting finding is that the ingestion of beets in a person with iron deficiency may cause red–tinged urine. In persons with normal iron levels, the beet pigment loses its color through a redox reaction with ferric ions.³