Generality
The total iron-binding capacity ( TIBC, from the English word " Total Iron Binding Capacity ") is a parameter that indicates how much the plasma proteins are able to bind this element and transport it into the circulatory stream.
Since transferrin (Tf) is the main plasma protein with iron binding capacity, TIBC values can be established to indirectly determine blood levels.
What's this
Transferrin is the main transport protein in the blood of oxidized iron (Fe3 +) .
In the blood, the Tf can be found both in free form ( transferrin unsaturated, that is not bound to iron), and in form linked to iron ( saturated transferrin ). The latter share coincides with the sideremia value.
The amount of transferrin available to iron binding and transport is reflected in the measurement of total iron binding capacity (TIBC), latent iron-binding capacity or transferrin saturation.
More in detail, TIBC is the indirect measure of the capacity of transferrin to bind iron. Although transferrinemia and TIBC are two different exams, they have an overlapping trend and essentially the same clinical significance. Therefore, at the discretion of the doctor, it may be sufficient to carry out only one of the two exams.
Why do you measure
Total iron-binding capacity (TIBC) is a prescribed test in patients who suspect iron metabolism abnormalities.
This analysis serves to determine the body's ability to transport the mineral. Since transferrin is the main iron-binding protein, the measurement of TIBC is a good approximation of the available Tb measurement.
TIBC is generally evaluated together with the determination of sideremia and ferritin, to get a more complete picture of iron metabolism .
Normal values
The normal values of total iron binding capacity vary between 240 and 450 μg / dL (43.0-80.6 μmol / L).
The relationship between serum iron and TIBC defines the saturation of transferrin, a figure usually expressed as a percentage.
- Saturation of transferrin = (sideremia / TIBC) x 100
- Normal values for men: 20-50%
- Normal woman values: 15-50%
TIBC Alta - Causes
High TIBC values usually indicate an iron deficiency associated with:
- Bleeding (including occult bleeding);
- Sideropenic anemias;
- Hypoxemic states;
- Use of oral contraceptives.
An increase in the total capacity to bind iron can also occur during pregnancy (increases in values are also typical in the third trimester of gestation), during lactation and in the child during growth.
TIBC Low - Causes
Low TIBC values can be found in case of:
- hemochromatosis;
- Some types of anemia due to iron accumulation;
- Malnutrition;
- Acute and chronic inflammatory states;
- Inflammation;
- Liver disease (such as cirrhosis, hepatitis, liver failure) or kidney disease (such as nephrotic syndrome, due to the loss of protein with urine);
- Chloramphenicol or ACTH therapy.
How to measure it
To carry out the examination of the total ability to bind the iron, the patient must undergo a blood test .
Preparation
The venous blood sampling useful to determine the TIBC is generally performed in the morning . Before undergoing the examination, the patient must observe a fast of at least 8 hours. During this period, a small amount of water can be taken. Furthermore, suspension of iron supplements is recommended for the two days preceding the analysis.
Interpretation of Results
- Low TIBC may lead to suspicion of iron overload, as occurs following repeated transfusions or hemochromatosis. Reduced values can also be found in the presence of anemia caused by chronic inflammatory infections and diseases, malnutrition, liver cirrhosis or nephrotic syndrome. A lowering of the values is also observable due to the intake of the hormone ACTH and the antibiotic chloramphenicol or during the use of cortisone.
- High TIBC generally indicates a deficiency or greater need for iron, as in the case of bleeding, iron deficiency anemia or hypoxemia. Oral contraceptives or pregnancy can also lead to an increase in the parameter.
However, it should be reiterated that this examination must be interpreted in an overall view of the tests concerning iron metabolism in the body. For example, in iron deficiency anemia (ie from iron deficiency), an initial reduction in ferritin is observed, followed by an increase in total iron-binding capacity and a reduction in sideremia.
| serum iron | TIBC / Transferrin | UIBC | % Transferrin saturated | Ferritin | |
| Iron Shortage | Bass | High | High | Bass | Bass |
| hemochromatosis | High | Bass | Bass | High | High |
| Chronic diseases | Bass | Bass | Low / Normal | Bass | Normal / High |
| Hemolytic anemia | High | Normal / Low | Low / Normal | High | High |
| Sideroblastic anemia | Normal / High | Normal / Low | Low / Normal | High | High |
| Poisoning by iron | High | Normal | Bass | High | Normal |
