TIBC measures all the proteins available for binding iron in circulation though it primarily reflects transferrin, the major carrier of iron in the blood. TIBC will increase in iron deficiency in an attempt to carry more available iron. However, it will decrease in chronic illness, liver disease, and inflammatory states.
Standard Range: 250.00 - 425.00 ug/dL (44.78 - 76.12 umol/L)
The ODX Range: 250.00 - 350.00 ug/dL (44.78 - 62.68 umol/L)
Low TIBC can be seen in inflammatory disease, cirrhosis, hypoproteinemia, chronic illness, and hemolytic, pernicious, and sickle cell anemias, as well as with the use of ACTH and chloramphenicol (Pagana 2021). Total iron binding capacity will be low in iron overload as transferrin levels decrease (Faruqi 2022).
High TIBC can be seen with iron deficiency anemia, pregnancy, and polycythemia vera. Drugs that can increase TIBC include oral contraceptives and fluorides (Pagana 2021).
Total iron binding capacity (TIBC) reflects circulating iron, mostly bound to transferrin, plus the additional amount of binding capacity that remains available to carry iron if needed (unsaturated binding capacity). In the event of iron insufficiency, the TIBC increases to provide more sites for binding and transporting iron. TIBC appears to reflect the function of the liver, where transferrin is produced, as opposed to being a direct measurement of iron metabolism (Pagana 2021).
TIBC may have some limits in diagnosing iron deficiency as it may only change significantly once iron stores have become depleted. Researchers recommend using ferritin as the gold standard for diagnosing iron deficiency in the absence of inflammation and infection (Asif 2016).
In one retrospective study of 80 iron deficiency anemia patients, TIBC was significantly higher in those with left ventricular remodeling, associated with an increased risk of ventricular dysfunction (Chen 2020).
Asif, Naveed et al. “Diagnostic Accuracy of Serum Iron and Total Iron Binding Capacity (TIBC) in Iron Deficiency State.” Journal of the College of Physicians and Surgeons--Pakistan : JCPSP vol. 26,12 (2016): 958-961.
Chen, Yan et al. “Total iron binding capacity (TIBC) is a potential biomarker of left ventricular remodelling for patients with iron deficiency anaemia.” BMC cardiovascular disorders vol. 20,1 4. 8 Jan. 2020, doi:10.1186/s12872-019-01320-3
Faruqi, Arjumand. and Shiva Kumar R. Mukkamalla. “Iron Binding Capacity.” StatPearls, StatPearls Publishing, 5 January 2022.
Pagana, Kathleen Deska, et al. Mosby's Diagnostic and Laboratory Test Reference. 15th ed., Mosby, 2021.