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Ferritin is a protein-iron complex found in all tissues, particularly liver, spleen, skeletal muscle and bone marrow. Ferritin molecules consist of 24 subunits of heavy and light chains. These subunits form a shell around a cavity in which crystalline iron is stored. Cellular accumulations of ferrin form aggregates that are taken up by lysosomes.As ferritin is degraded by lysosomal proteases, it forms hemosiderin.

Serum ferritin is the single most useful test for assessing total body iron stores. Serum ferritin originates from intracellular stored excess iron not used for hemoglobin synthesis. The amount of ferritin in plasma directly reflects the total body iron stored as ferritin in tissues. In iron deficiency, serum ferritin is often lower than 12 ng/mL, whereas it may exceed 1000 ug/mL in iron overload.

Serum ferritin levels are low in patients with iron deficiency anemia, acute blood loss and in infants. A serum ferritin level less than 15 - 20ng/mL confirms that iron deficiency is present (98% specificity, 75% sensitivity). Ferritin levels are increased independently of iron storage in patients with hepatic necrosis, acute inflammatory conditions, with malignant tumors of lung, breast, pancreas and liver and excess iron and transfusion therapy.These disorders may mask iron deficiency. In these situations, a ferritin level of less than 30 - 50ng/mL may be considered indicative of iron deficiency.

Ferritin should be used as confirmatory test for primary iron overload in patients who have had an elevated transferrin saturation on two separate occasions. A serum ferritin level above 200 ng/mL for premenopausal women or 400 ng/mL for men (in the absence of inflammation, cancer or hepatitis) supports the diagnosis of hereditary hemochromatosis. Routine therapeutic phlebotomy should be initiated if the serum ferritin level is >300 ng/mL in men or >200 ng/mL in women. Phlebotomy of one unit of blood is done weekly until the serum ferritin level falls to 10 to 20 ng/mL. Therapeutic phlebotomy should be continued lifelong to keep the serum ferritin level below 50 ng/mL.

Reference range is 20 ? 300 ng/mL in men and 20 ? 200 ng/mL in women.

Specimen requirement is one SST tube of blood.

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