TIBC & UIBC, Transferrin

Also known as: Iron binding capacity; IBC; Serum Iron-Binding capacity; Siderophilin

Formal name: Total iron-binding capacity; Unsaturated iron-binding capacity; Transferrin; Transferrin saturation

Related tests: Iron tests, Serum iron, Ferritin, Zinc Protoporphyrin (ZPP), Transferrin receptor

How is it used?

Total iron-binding capacity (TIBC) is most frequently used along with a serum iron test to evaluate people suspected of having either iron deficiency or iron overload. These two tests are used to calculate the transferrin saturation, a more useful indicator of iron status than just iron or TIBC alone. In healthy people, about 20-40% of available sites in transferrin are used to transport iron.

In iron deficiency, the iron level is low, but the TIBC is increased, thus transferrin saturation becomes very low. In iron overload states, such as hemochromatosis, the iron level will be high and the TIBC will be low or normal, causing the transferrin saturation to increase. UIBC may be ordered as an alternative to TIBC.

It is customary to test for transferrin (instead of TIBC or UIBC) when evaluating a patient's nutritional status or liver function. Because it is made in the liver, transferrin will be low in patients with liver disease. Transferrin levels also drop when there is not enough protein in the diet, so this test can be used to monitor nutrition.

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When is it ordered?

TIBC or UIBC may be ordered along with serum iron when it appears that a person has iron deficiency or overload. One or more tests may be ordered when there are signs of anemia, especially when red blood cells are microcytic and hypochromic, and the hemoglobin and hematocrit levels are low.

The most common symptoms of anemia include:

Chronic fatigue/tiredness
Dizziness
Weakness
Headaches

When a doctor suspects that a person may have iron overload or when a person has a family history of hemochromatosis, iron and TIBC may be ordered along with a ferritin test to see if excessive amounts of iron are present in the blood, or if iron stores are elevated. Symptoms of iron overload will vary from person to person and tend to worsen over time. They are due to iron accumulation in the blood and tissues. Symptoms may include:

Joint pain
Fatigue, weakness
Lack of energy
Abdominal pain
Loss of sex drive
Heart problems

However, many people have no initial symptoms.

Iron and TIBC are also ordered in cases of suspected iron poisoning, which is most common in children who accidentally overdose with vitamins or other supplements containing iron.

A transferrin test may be ordered along with other tests such as prealbumin when a doctor wants to evaluate or monitor a person's nutritional status.

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What does the test result mean?

The results of transferrin tests, TIBC, or UIBC are usually evaluated in conjunction with other iron tests. A summary of the changes in iron tests seen in various diseases of iron status is shown in the table below.

Disease	Iron	TIBC/Transferrin	UIBC	%Transferrin Saturation	Ferritin
Iron Deficiency	Low	High	High	Low	Low
Hemochromatosis	High	Low	Low	High	High
Chronic Illness	Low	Low	Low/Normal	Low	Normal/High
Hemolytic Anemia	High	Normal/Low	Low/Normal	High	High
Sideroblastic Anemia	Normal/High	Normal/Low	Low/Normal	High	High
Iron Poisoning	High	Normal	Low	High	Normal

A high TIBC, UIBC, or transferrin usually indicates iron deficiency, but they are also increased in pregnancy and with use of oral contraceptives. A low TIBC, UIBC, or transferrin may occur if you have hemochromatosis, certain types of anemia in which iron accumulates, malnutrition, inflammation, liver disease, or nephrotic syndrome, a kidney disease that causes loss of protein in urine.

Transferrin saturation is decreased with iron deficiency and increased when excess amounts of iron are present, as in iron overload or poisoning.

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Is there anything else I should know?

People with hemolytic diseases may have increased iron concentrations in their blood because hemoglobin is released from red blood cells during .

Recent blood transfusions can affect test results. Multiple blood transfusions can sometimes lead to iron overload.

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