Total iron-binding capacity
Total iron-binding capacity or sometimes transferrin iron-binding capacity is a medical laboratory test that 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 unsaturated iron-binding capacity or UIBC. The UIBC is calculated by subtracting the serum iron from the TIBC.
Interpretation
Taken together with serum iron and percent transferrin saturation clinicians usually perform this test when they are concerned about anemia, iron deficiency or iron deficiency anemia. However, because the liver produces transferrin, alterations in function 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 can also be a useful indicator.
| Condition | Serum iron | Transferrin and TIBC | Percent transferrin saturation |
| Iron deficiency anemia | Low | High. The liver produces more transferrin, presumably attempting to maximize use of the little iron that is available. | Low, as there is insufficient iron. |
| Anemia of chronic disease | Low, as the body holds iron intracellularly with ferritin. | Low. The body produces less transferrin, presumably to keep iron away from pathogens that require it for their metabolism. This is mainly regulated by increased hepcidin production. | Normal |
| Pregnancy or use of hormonal contraception, but without iron deficiency | Normal | High. The liver increases the production of transferrin, thus raising TIBC. | Low, as there is excess transferrin with normal serum iron levels. |
These examples demonstrate that to properly understand a value for TIBC, one also must know the serum iron, the percent transferrin saturation, and the individual clinical situation. In modern laboratory testings, serum ferritin levels are generally accepted as reliable single indicators of the presence of iron deficiency.
Usual values
Laboratories often use different units of measurement and "normal" may vary by population and the laboratory techniques used. Look at the individual laboratory reference values to interpret a specific test. Example reference ranges are:- Serum iron: Male 65–177 μg/dL ; Female 50–170 μg/dL
- TIBC: 250–370 μg/dL
- Transferrin saturation: Male 20–50%; Female 15–50%
- Serum ferritin: Male 20-250 μg/mL, Female 15-150 μg/mL