Of the large amount of iron that is stored in the body, only a small fraction is actually transported in the serum. The protein that does this transporting of iron around the body is called transferrin. A single molecule of transferrin can carry 2 molecules of iron, and in a normal person, only about 30% of these spots for iron are filled.
Total iron-binding capacity (TIBC) is a medical laboratory test which measures the blood's capacity to bind iron with transferrin. It is performed by drawing blood and measuring the maximum amount of iron that it can carry, which indirectly measures transferrin. since transferrin is the most dynamic carrier. TIBC is less expensive than a direct measurement of transferrin. The TIBC should not be confused with the UIBC, or "unsaturated iron binding capacity". The UIBC is calculated by subtracting the serum iron from the TIBC.
This test is performed when Physicians are concerned about anemia, iron deficiency or iron deficiency anemia. However, because the liver produces transferrin, alterations in function (such as cirrhosis, hepatitis, or liver failure) must be considered when performing this test. It can also be an indirect test of liver function, but is rarely used for this purpose.
The percent transferrin saturation (i.e., the result of the formula of serum iron/TIBC x 100) can also be a useful indicator.
