Clinical and Interpretive

Measurement of ferritin is useful in diagnosing iron deficiency and iron-overload conditions. Ferritin is a high-molecular-weight protein that contains approximately 20% iron. It occurs normally in almost all tissues of the body but especially in hepatocytes and reticuloendothelial cells, where it serves as an iron reserve. Ferritin is also present in the serum in minute amounts, where it appears to reflect iron stores in normal individuals.

Ferritin plays a significant role in the absorption, storage, and release of iron. As the storage form of iron, ferritin remains in the body tissues until it is needed for erythropoiesis. When needed, the iron molecules are released from the apoferritin shell and bind to transferrin, the circulating plasma protein that transports iron to the erythropoietic cells.

A low serum ferritin value is thought to be the best laboratory indicator of iron depletion. Virtually all patients with low serum iron and low ferritin have iron deficiency. Serum ferritin is clinically useful in distinguishing between iron-deficiency anemia (serum ferritin levels diminished) and “anemia of chronic disease” (serum ferritin levels usually normal or elevated). Serum ferritin is a good screening test in separating erythrocyte microcytosis due to iron deficiency (low values) from microcytosis related to thalassemia minor (normal or high values). An iron-depletion state with a decreased serum ferritin value is quite common among menstruating and reproductively active females and in children.

Ferritin is an acute phase reactant. A normal serum ferritin value, therefore, cannot be used to exclude iron deficiency if a hepatic, malignant, or inflammatory condition is present.

A high serum ferritin value is seen in hemochromatosis and other iron-overload states, as well as acute hepatitis, Gaucher disease, malignancies, and chronic inflammatory disorders. Slight-to-moderate elevation occurs in many malignancies and in chronic inflammatory disorders.

A normal serum ferritin value cannot be used to exclude iron deficiency if a hepatic, malignant, or inflammatory condition is present (ferritin is an acute phase reactant).