Iron-Binding Capacity, Total (TIBC)

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Subject: Iron-Binding Capacity, Total (TIBC)

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Definition

  • TIBC measures the blood's capacity to bind iron with transferrin (TRF). One milligram of TRF binds to 1.25 μg of iron, and, therefore, a serum TRF level of 300 mg/dL is equal to TIBC of (300 × 1.25) 375 μg/dL. TIBC is an indirect way of assessing TRF level. TIBC correlates with serum TRF, but the relationship is not linear over the wide range of TRF values and is disrupted in diseases affecting transferrin-binding capacity and iron-binding proteins. TIBC should not be confused with unsaturated binding capacity (UIBC), where UIBC = TIBC minus serum iron (μg/dL).

  • Normal range: 255–450 μg/dL.

Use

  • Differential diagnosis of anemias

  • Should always be performed whenever serum iron is done to calculate percent saturation for diagnosis of iron deficiency

  • Screening for iron overload

  • Acute hepatitis

  • Late pregnancy

Interpretation

Increased In

  • Iron deficiency

  • Acute and chronic blood loss

  • Acute liver damage

  • Late pregnancy

  • Progesterone birth control pills

Decreased In

  • Hemochromatosis

  • Cirrhosis of the liver

  • Thalassemia

  • Anemias of infection and chronic diseases (e.g., uremia, RA, some neoplasms)

  • Nephrosis

  • Hyperthyroidism

Limitations

 
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