Examinations
Examinations
Iron is an essential element in the human body. It is a key component of hemoglobin, which is found in red blood cells and ensures the transport of oxygen from the lungs to organs and tissues. Iron is also present in the muscle protein myoglobin and certain enzymes. It is obtained from food and transported throughout the body by transferrin, a specialized protein produced by the liver.
Normally, the body contains 4–5 g of iron, with about 3–4 mg (0.1% of the total) circulating in the blood bound to transferrin. The amount of transferrin depends on liver function and nutritional status. Typically, one-third of transferrin’s binding sites are occupied by iron, while the remaining two-thirds remain as a reserve.
To determine the total iron-binding capacity (TIBC) of serum, a specific amount of iron is added to a serum sample to fully saturate all available transferrin binding sites. The total amount of iron bound to transferrin is then measured. TIBC reflects iron deficiency status and accurately represents transferrin levels in the blood.
Although serum iron levels fluctuate significantly from day to day and even within the same day (especially in the morning), iron-binding capacity remains relatively stable.
Purpose of Testing
Iron-binding capacity and iron levels are tested to detect iron deficiency or excess in the body.
- Sample: Blood drawn from the antecubital vein.
- Fasting is required for at least 12 hours before the test (only water is allowed).
- Total iron-binding capacity (TIBC): The total amount of iron that can bind to proteins in the blood.
- Unsaturated iron-binding capacity (UIBC): The reserve capacity of transferrin for iron binding.
- Transferrin saturation coefficient: Calculated based on plasma iron levels and binding properties, indicating the percentage of transferrin saturated with iron.
Interpretation of Results
Iron-binding capacity results are usually assessed along with other iron metabolism parameters for a more comprehensive evaluation.
Causes of Increased Iron-Binding Capacity:
- Iron-deficiency anemia – The most common cause of low iron levels, usually due to chronic blood loss or insufficient dietary intake of meat products.
- Third trimester of pregnancy – Serum iron levels decrease due to increased iron demand.
- Acute hepatitis – Liver damage affects iron metabolism and transferrin levels.
Causes of Decreased Iron-Binding Capacity:
- Chronic diseases – Conditions such as systemic lupus erythematosus (SLE), rheumatoid arthritis, tuberculosis, bacterial endocarditis, Crohn’s disease, and others.
- Hypoproteinemia – Caused by malabsorption disorders, chronic liver disease, burns, leading to decreased protein levels in the body.
- Hereditary hemochromatosis – A genetic disorder in which excess iron is absorbed from food and accumulates in various organs, causing damage.
- Thalassemia – A genetic disorder causing anemia due to abnormal hemoglobin structure.
- Liver cirrhosis – Affects the liver’s ability to regulate iron levels.
- Glomerulonephritis – Inflammation of the kidneys, leading to disruptions in iron metabolism.
- Frequent blood transfusions, intramuscular iron injections, or iron supplement overdose – Can lead to excessive iron accumulation in the body.