Clinlab Navigator

Ferritin

Ferritin is a protein-iron complex found in all tissues, particularly liver, spleen, skeletal muscle and bone marrow. Ferritin functions to store iron intracellularly in a nontoxic form and release it in a controlled fashion. Ferritin is a 450 kDa protein comprised 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 ferritin form aggregates that are taken up by lysosomes. As ferritin is degraded by lysosomal proteases, it forms hemosiderin.

Serum ferritin originates primarily from excess iron stored in macrophages that is not used for hemoglobin synthesis. The amount of ferritin in plasma directly reflects the total body iron stored as ferritin in tissues. Serum ferritin is usually measured to identify patients with iron deficiency or iron overload syndromes. A serum ferritin less than 10 to 15 mg/L is 99% specific for making a diagnosis of iron deficiency.

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 49 ng/mL is consistent with 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.

In addition to iron overload, elevated ferritin concentration can be seen in a variety of conditions including iron overload syndromes, infection, inflammatory disorders, malignancy, liver failure, and renal failure.

In the pediatric population, extremely elevated ferritin is highly sensitive and specific for hemophagocytic lymphohistiocytosis (HLH). A maximum ferritin level higher than 10 000 ng/mL has a 90% sensitivity and 98% specificity for HLH. However, in adults a serum ferritin elevation more than 5 times this level (50,000 ng/mL) is associated with a variety of disorders such as renal failure, hepatocellular injury, infections, and hematologic malignancies. Highly elevated ferritin is not predictive of HLH in adults.

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

Specimen requirement is one SST tube of blood.

References

Guyatt GH, Oxman AD, Ali M, Willan A, McIlroy W, Patterson C. Laboratory diagnosis of iron- deficiency anemia: an overview. J Gen Intern Med. 1992;7(2):145-153.

AddThis Social Bookmark Button