What is Immunoglobulin - IgE Total?

Also Known As: Quantitative IgE

Formal Name: Immunoglobulin E

Immunoglobulin E (IgE) is an antibody that is produced by the body’s immune system in response to a perceived threat. It is one of five classes of immunoglobulins (A, G, M, D, and E) and is normally present in the blood in very small amounts. This test measures the amount of IgE in the blood.

Immunoglobulins are proteins that play a key role in the body’s immune system. They are produced by specific immune cells called plasma cells. Immunoglobulins are produced in response to bacteria, viruses, and other microorganisms as well as substances that are recognized as “non-self” or present harmful antigens to the immune system.

Immunoglobulin E is associated with allergic responses, including asthma, and to a lesser degree with immunity to parasites. With allergies, the body overreacts to one or more substances in the environment called allergens that do not typically cause a response in other people. Someone may develop an allergy when that person is exposed to an allergen, such as plant pollen, peanuts, eggs, strawberries, bee venom, and hundreds of other potential substances.

During initial exposure, also called sensitization, an allergic person produces an IgE specifically directed against that allergen. IgE binds to specialized white blood cells, resulting in the release of a number of substances, including histamine. In allergic/asthmatic people, this can cause constriction of the bronchi in the lungs. These substances are also responsible for the running nose, itchy eyes, and skin itching that occur in people with allergies.

Each time an allergic person is exposed to a specific allergen(s) after the initial exposure, IgE is rapidly produced, increasing to levels that trigger an allergic reaction. The severity of the reaction and symptoms associated with each episode can range from a localized reddening and itching of the skin to respiratory distress to vomiting and diarrhea, and in some cases to life-threatening anaphylaxis. The severity will vary from person to person, can vary from episode to episode, and may worsen over time.

The total IgE test measures the overall quantity of immunoglobulin E in the blood, not the amount of a specific type. It can be used to detect an allergic response in the body rather than a specific allergy. This test may complement the information provided by allergy tests that detect allergen-specific IgE.

How is the sample collected for testing?

A blood sample is obtained by inserting a needle into a vein in the arm.

Is any test preparation needed to ensure the quality of the sample?

No test preparation is needed.

How is it used?

The total IgE test may be used to help screen for and detect allergic diseases. It measures the overall quantity of immunoglobulin E in the blood. It may be ordered by itself, before, or along with allergen-specific IgE tests, depending upon whether or not a person or healthcare practitioner has identified potential substances to which the person may be allergic.

Immunoglobulin E (IgE) is an antibody that is produced by the body’s immune system in response to a perceived threat. It is one of five classes of immunoglobulins and is normally present in the blood in very small amounts. IgE is associated with allergic responses, including asthma, and to a lesser degree with immunity to parasites. (For more, see the “What is being tested?” section.)

IgE can be increased with parasitic infections, so a total IgE test is sometimes used as a screening test if parasitic infection is suspected.