What is Total Iron-Binding Capacity (TIBC) test?

A total iron-binding capacity (TIBC) test measures the total amount of proteins in your blood that can bind to iron.

Iron is an important element that your body requires to make haemoglobin - a protein which carries oxygen throughout the body. Thus, a reduction in the amount of iron will lead to reduced haemoglobin. Approximately 65% of iron is carried in the red blood cells by haemoglobin. However, iron is also found in several locations of the body. About 4% of iron is found in skeletal muscles. Ferritin, a protein present in the spleen, liver and bone marrow, contains 30% of iron. The remaining iron is carried in the blood, bound to iron-binding proteins.

Transferrin is the main iron-binding protein that carries and transports iron throughout the body. However, only one-third of the total transferrin in the blood is used to carry iron. Thus, the blood can have a lot more iron than it normally has. This is known as the unsaturated iron-binding capacity (UIBC). TIBC is the sum of UIBC and the iron present in the blood.

TIBC measurement is an indirect but accurate method to measure transferrin. In individuals with iron deficiency, TIBC levels are found to be higher than the normal values; and in conditions which increase the iron levels in your blood, TIBC levels will be normal or low.

(Read more: Iron test)

  1. Why is a Total Iron-Binding Capacity (TIBC) test performed?
  2. How do you prepare for a Total Iron-Binding Capacity (TIBC) test?
  3. How is a Total Iron-Binding Capacity (TIBC) test performed?
  4. Total Iron-Binding Capacity (TIBC) test results and normal range

Your healthcare provider may ask you to undergo this test if he/she thinks that your iron levels are abnormal. They may do this test to check your nutrition and diet or to look for conditions that may cause your iron levels to be abnormal, such as liver problems, pregnancy or increased blood loss.

Symptoms of iron deficiency include the following:

  • Frequent infections
  • Swelling in the tongue
  • Delayed mental development in children
  • Weakness
  • Difficulty to keep up at work or school
  • Feeling cold all the time

Symptoms of too much iron are as follows:

Your healthcare provider may ask you to take this test in the morning after fasting overnight. This is because the iron levels are nearest to the normal value in the morning and decrease as the day progresses. 

Inform your healthcare provider about all vitamins, herbs, supplements and medicines (including over-the-counter drugs and illicit drugs) that you are consuming. Alcohol and drugs such as antibiotics, birth control pills, fluorides, adrenocorticotropic hormone and chloramphenicol may affect the result of this test. Your doctor may ask you to stop taking certain medicines or he/she will change the course of some medicines.

Tell your doctor if you have a hemolytic disease like hemolytic anaemia since you may have a high blood iron content.

Also, women should inform the doctor if they are on their period as their iron count may drop during this time.

The laboratory technician will require a blood sample to perform this test. The sample would be withdrawn from a vein in your arm. You may feel slight discomfort at the site as the needle goes in, it may even turn sore for a while after the test. However, it is nothing to worry about. Talk to your doctor if the discomfort persists.

Results of this test may differ according to an individual’s age, sex, health history and the method used for the test.

Normal results:

The TIBC of a healthy person (both women and men) is in the range of 250-450 mcg/dL (micrograms/decilitre).

Abnormal results:

Higher than the normal TIBC values indicate low iron levels in the body. It may be seen in the following conditions:

  • Iron deficiency anaemia and other types of anaemia
  • Long-standing infections or diseases
  • Blood loss over time
  • Last three months of pregnancy

Decreased TIBC levels are seen in the following conditions:

  • Haemolytic anaemia, a condition that is caused when the red blood cells are being destroyed quickly
  • Inflammation
  • A lower-than-normal level of protein in the blood (hypoproteinaemia)
  • Iron overload, such as from haemochromatosis
  • Nephrotic syndrome (kidney damage)
  • Liver diseases
  • Malnutrition
  • Sickle-cell anaemia, a disease of red blood cells
  • Pernicious anaemia, a decrease in red blood cells from the intestines not properly absorbing vitamin B12 

(Read more: Vitamin B12 deficiency symptoms)

Disclaimer: All results must be clinically correlated with the patient’s complaints to make a complete and accurate diagnosis. The above information is provided from a purely educational point of view and is in no way a substitute for medical advice by a qualified doctor.

References

  1. Pagana KD, Pagana TJ, Pagana TN. Mosby’s Diagnostic and Laboratory Test Reference. 14th ed. Misouri: Elsevier. 2019. Pp:546-548.
  2. University of Rochester Medical Center [Internet]. Rochester (NY): University of Rochester Medical Center; Iron and Total Iron-Binding Capacity
  3. Wilson DD. McGraw-Hill’s Manual of Laboratory and Diagnostic Tests. Laboratory and Diagnostic Tests. 2008. Pp:558,559.
  4. Wang W, Knovich MA, Coffman LG, Torti FM, Torti SV. Serum ferritin: past, present and future. Biochim Biophys Acta. 2010 Aug;1800(8):760-769. PMID: 20304033.
  5. National Health Service [internet]. UK; Total iron-binding capacity (TIBC) and transferrin test
  6. National Health Service [internet]. UK; Blood Tests
  7. Chernecky CC, Berger BJ. Iron (Fe) and total iron-binding capacity (TIBC)/transferrin - serum. In: Chernecky CC, Berger BJ, eds. Laboratory Tests and Diagnostic Procedures. 6th ed. Philadelphia, PA: Elsevier; 2013:691-692.
  8. Brittenham GM. Disorders of iron homeostasis: iron deficiency and overload. In: Hoffman R, Benz EJ, Silberstein LE, et al, eds. Hematology: Basic Principles and Practice. 7th ed. Philadelphia, PA: Elsevier; 2018:chap 36.
  9. National Institute of Diabetes and Digestive and Kidney Diseases [internet]: US Department of Health and Human Services; Nephrotic Syndrome in Adults
  10. National Heart, Lung, and Blood Institute [Internet]. Bethesda (MD): U.S. Department of Health and Human Services; Sickle Cell Disease
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