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Legionella Antibody

Does this test have other names?

Legionnaires' disease antibody test, Legionella antibody assay

What is this test?

This test looks for an antibody that may be in your blood if you have Legionnaires' disease.

Legionnaires' disease is a type of pneumonia or serious lung infection caused by bacteria called Legionella.

Antibodies are proteins that your immune system makes to fight infection or foreign invaders. The bacteria and the disease get their name because of an outbreak that occurred among people attending an American Legion convention in Philadelphia in 1976.

Why do I need this test?

You might have this test to see if your doctor suspects that you have Legionnaires' disease or a milder form of infection known as Pontiac fever. Symptoms of Legionnaires' disease include:

  • High fever

  • Chills

  • Cough

  • Muscle aches

  • Headaches

Symptoms may begin two days to two weeks after you are exposed to the bacteria.

You may need this test repeated after several weeks to confirm your diagnosis or to see whether you have recovered.

What other tests might I have along with this test?

Your doctor might also order a chest X-ray to diagnose pneumonia. He or she might also take a sample of your mucus or lung tissue for a culture test, and order a urine test to look for Legionella.

What do my test results mean?

Many things may affect your lab test results. These include the method each lab uses to do the test. Even if your test results are different from the normal value, you may not have a problem. To learn what the results mean for you, talk with your health care provider.

Normal results are negative, meaning that no Legionella antibody was found in your blood. A positive result means that Legionella antibodies were found and that you may have Legionnaires' disease.

How is this test done?

The test requires a blood sample, which is drawn through a needle from a vein in your arm.

Does this test pose any risks?

Taking a blood sample with a needle carries risks that include bleeding, infection, bruising, or feeling dizzy. When the needle pricks your arm, you may feel a slight stinging sensation or pain. Afterward, the site may be slightly sore.

What might affect my test results?

If the test is done too early after you are infected, you may have a false-negative result.

How do I get ready for this test?

You don't need to prepare for this test.