Is total iron binding capacity (Total Iron-Binding Capacity, TIBC) low or high in iron deficiency anemia?

From the Guidelines

In iron deficiency anemia, total iron binding capacity (TIBC) is high. This occurs because the body responds to low iron levels by increasing the production of transferrin, the protein responsible for transporting iron in the bloodstream, as noted in the study by the Centers for Disease Control and Prevention 1. When iron stores are depleted, the liver synthesizes more transferrin in an attempt to capture any available iron, resulting in an elevated TIBC. Some key points to consider include:

• TIBC is a measure of the iron-binding capacity within the serum and reflects the availability of iron-binding sites on transferrin, as explained in the study 1.
• TIBC increases when serum iron concentration (and stored iron) is low and decreases when serum iron concentration (and stored iron) is high, according to the study 1.
• Factors other than iron status can affect results from this test, such as inflammation, chronic infection, malignancies, liver disease, nephrotic syndrome, and malnutrition, which can lower TIBC readings, and oral contraceptive use and pregnancy can raise the readings, as mentioned in the study 1. The combination of low serum iron and high TIBC creates a low transferrin saturation percentage, which is a characteristic laboratory finding in iron deficiency anemia, helping to distinguish it from other types of anemia.

From the Research

Iron Binding Capacity in Iron Deficiency Anemia

• Iron binding capacity, also known as total iron binding capacity (TIBC), is a measure of all proteins available for binding mobile iron, including both transferrin that is already bound to iron and transferrin that is not yet bound to iron 2.
• In iron deficiency anemia, TIBC is typically high, as the body produces more transferrin to try to capture as much iron as possible from the diet 3, 4.
• Studies have shown that TIBC is a useful indicator of iron deficiency, with high TIBC levels often indicating iron deficiency anemia 4, 5.
• One study found that TIBC outperformed serum iron and transferrin saturation in predicting iron deficiency, with a mean area under the ROC curve of 0.94 4.
• Another study found that TIBC was increased in patients with iron deficiency anemia and left ventricular remodeling, suggesting that TIBC may be a potential biomarker for cardiac remodeling in patients with iron deficiency anemia 6.

Diagnostic Utility of TIBC

• TIBC is often used in conjunction with other tests, such as serum ferritin and transferrin saturation, to diagnose iron deficiency anemia 2, 3.
• However, one study found that serum iron and TIBC give no additional information in the diagnosis of iron deficiency anemia if serum ferritin is available 3.
• Another study found that transferrin or TIBC measurement outperformed iron measurement and saturation index in identifying unequivocal iron deficiency 4.

Clinical Implications

• High TIBC levels in iron deficiency anemia may indicate a need for iron supplementation or other treatments to address the underlying cause of the iron deficiency 2, 6.
• TIBC may be a useful biomarker for monitoring the effectiveness of treatment for iron deficiency anemia, particularly in patients with cardiac remodeling 6.