TIBC measures the bloods capacity to bind iron with transferrin (TRF). One milligram of TRF binds to 1.25 Ž ¼g of iron, and, therefore, a serum TRF level of 300 mg/dL is equal to TIBC of (300 ƒ — 1.25) 375 Ž ¼g/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 ( Ž ¼g/dL).
Normal range: 255 " “450 Ž ¼g/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
Estrogens and oral contraceptives increase TIBC levels.
Asparaginase, chloramphenicol, corticotropin, cortisone, and testosterone decrease the TIBC levels.