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Iron & Total Iron Binding Capacity (TIBC) Test

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About Our Iron & Total Iron Binding Capacity (TIBC) Test

Our Total Iron Binding Capacity (TIBC) Test includes an Iron Test and is used to see if there is too much or too little iron in the blood. Iron moves through the blood attached to a protein called transferrin. The TIBC Test is often used to differentiate between anemia types and gives more iron statistics than the Iron Test alone.

Disorders of iron homeostasis rank among the most common of human diseases. These include states of either iron deficiency (inadequate adsorption or increased loss) or iron overload (normal erythropoiesis but iron exceeds iron binding capacity of transferrin or catabolism of red cells causes iron overload). Serum iron levels fluctuate considerably in response to various pathologic as well as physiologic conditions, and as such, require additional studies to assess a patient's iron status. Blood levels for iron, total iron binding capacity (TIBC), and Ferritin facilitate interpretation.

Iron is transported in the blood by transferrin (essentially all circulating iron is bound to transferrin). The TIBC is the amount of iron needed to 100% saturate transferrin (thus an indirect measurement of transferrin). The assay for iron measures the amount of iron which is bound to transferrin.

Clinical Interpretation of TIBC

  • Support a diagnosis of iron deficiency
    • Due to inadequate intake, malabsorption, or altered metabolism
    • Due to blood loss
  • Support a diagnosis of iron overload
    • Primary: Hereditary hemochromatosis (HH) where overload is caused by increased gastrointestinal iron absorption (erythropoiesis is normal); excessive iron is deposited in the liver and other organs causing fibrosis if untreated
    • Secondary: Hemosiderosis where iron overload is caused by a variety of conditions including anemias due to ineffective erythropoiesis (eg, thalassemias), repeated blood transfusion, excessive parenteral or oral replacement, etc
  • Aid in distinguishing iron deficiency from chronic disease when the serum iron is low
  • Monitor iron replacement therapy (transferrin saturation)
  • Confirm diagnosis of iron toxicity (child overdose via vitamin ingestion) and monitor levels
  • Monitor iron levels in patients undergoing dialysis
  • To follow treatment for iron overload with deferoxamine or with regimen of recombinant human erythropoietin and phlebotomy

Interpreting Low and High Levels

Increased serum (plasma) iron:

  • Iron is increased in hemosiderosis, hemolytic anemias (especially thalassemia), sideroblastic anemias, hepatitis, acute hepatic necrosis, hemochromatosis, and with inappropriate iron therapy.
  • Some patients who receive multiple transfusions (eg, some hemolytic anemias, thalassemia, renal dialysis patients) will have increased serum iron levels.
  • Iron may reach high levels with iron poisoning, which presents with emesis and severe abdominal pain. Metabolic acidosis with increased anion gap, leukocytosis, and hyperglycemia may be found with increased bilirubin, AST, ALT, and LD.

Decreased serum (plasma) iron:

  • Serum (plasma) iron is decreased with insufficient dietary iron, chronic blood loss (including the hemolytic anemias, paroxysmal nocturnal hemoglobinuria), inadequate absorption of iron; and impaired release of iron stores as in inflammation, infection, and chronic diseases.
  • In recovery from pernicious anemia, especially just after B12 dose, iron levels are low.
  • Serum iron is reported to drop with acute infarct of myocardium.

Increased TIBC:

  • Iron-deficiency, oral contraceptives, late pregnancy

Decreased TIBC:

  • Hypoproteinemia from many causes, including kwashiorkor, inflammation, hemochromatosis, hemosiderosis, thalassemia, hyperthyroidism, nephrotic syndrome, anemia of chronic disease, hemolytic anemia

In cases of low or abnormal CBC Test results where the hemoglobin and/or hematocrit levels are deficient, the TIBC Test and/or Iron Test may be ordered.

Medically Reviewed by: 2019-11-09

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