Iron Tests Health Article

Definition

Iron tests consist of four assays performed on serum or plasma to aid in the diagnosis and treatment of iron deficiency or iron overload. These tests are serum iron, total iron binding capacity (TIBC), serum ferritin, and serum transferrin. Iron is an essential trace element needed for the production of hemoglobin as well as the function of cytochromes (compound molecules that are important in cell respiration) and certain enzymes. Iron in plasma is almost entirely bound to transport proteins. The total iron binding capacity (TIBC) is the maximum amount of iron that these proteins can bind. Transferrin, a beta globulin (molecular weight 75,000) is the principal transport protein for iron in plasma. Therefore, the TIBC is determined mainly by the concentration of serum transferrin. Iron is stored in the epithelial cells of the gastrointestinal tract and in the reticuloendothelial cells of the liver, spleen, and bone marrow. Ferritin is the principal form of storage iron. It consists of a protein (apoferritin) and iron in the form of ferric salts.

Purpose

Serum or plasma iron tests are used for the following purposes:

• To help in the differential diagnosis of anemias. Iron deficiency anemia is the most common form of anemia worldwide and is quite common in the United States—especially in multiparous females, young children, and persons with chronic intestinal bleeding.
• To assess the severity of anemia and monitor the treatment of patients with chronic anemia.
• To diagnose conditions of iron excess, including iron ingestion, thalassemia, hemosiderosis, and hemochromatosis. Hemosiderosis and hemochromatosis are conditions produced by excessive iron stores in the tissues. Hemosiderosis, which results from repeated blood transfusions, is not associated with tissue damage. Hemochromatosis, which is a disorder of iron absorption, can cause painful joints, skin bronzing, diabetes, and liver damage if the iron concentration in the body is not lowered. Hemachromatosis is still underdiagnosed because of its long latency period and lack of awareness on the part of medical professionals.

A serum iron test can be used without the others to evaluate cases of iron poisoning.