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Toxoplasma test

Definition

The toxoplasma test looks for antibodies in the blood to a parasite called Toxoplasma gondii. The parasite causes an infection called toxoplasmosis, which poses a danger to a developing baby if a pregnant women gets it. It is also dangerous in people with AIDS.

Alternative Names

Toxoplasma serology; Toxoplasma antibody titer

How the test is performed

A blood sample is needed. For information on how this is done, see: Venipuncture

The sample is sent to a lab, where antibodies to Toxoplasma gondii are detected using several tests, including an indirect fluorescent antibody test, ELISA, and the Sabin-Feldman dye test.

How to prepare for the test

There is no special preparation for the test.

How the test will feel

When the needle is inserted to draw blood, you may feel moderate pain, or only a prick or stinging sensation. Afterward, there may be some throbbing.

Why the test is performed

The test is done soon after pregnancy to detect toxoplasmosis infection in a newborn baby. It may also be used to screen pregnant women for the antibodies to the parasite.

The presence of antibodies before pregnancy probably protects a developing baby against toxoplasmosis at birth. However, antibodies that develop during pregnancy may mean the mother and baby are infected. This increases the risk of miscarriage or birth defects.

This test may also be done if you have:

  • Unexplained lymph node swelling
  • An unexplained rise in the blood white cell (lymphocyte) count
  • HIV and have symptoms of a brain infection (including headache, seizures, weakness, and speech or vision problems)
  • Inflammation of the back part of the eye (chorioretinitis)

Normal Values

A titer (measurement of the concentration in a sample) of less than 1:16 indicates that there has likely never been an infection with toxoplasma gondii.

What abnormal results mean

A titer of 1:16 - 1:256 is a sign that you have probably been infected with the parasite sometime in the past.

A titer of greater than 1:1,024 may be a sign of an active toxoplasmosis infection.

The examples above are common measurements for results of these tests. Normal value ranges may vary slightly among different laboratories. Some labs use different measurements or test different samples. Talk to your doctor about the meaning of your specific test results.

What the risks are

Veins and arteries vary in size from one patient to another and from one side of the body to the other. Obtaining a blood sample from some people may be more difficult than from others.

Other risks associated with having blood drawn are slight but may include:

  • Excessive bleeding
  • Fainting or feeling light-headed
  • Hematoma (blood accumulating under the skin)
  • Infection (a slight risk any time the skin is broken)

References

Montoya JG, Boothroyd JC, Kovacs JA. Toxoplasma gondii. In: Mandell GL, Bennett JE, Dolin R, eds. Principles and Practice of Infectious Diseases. 7th ed. Philadelphia, Pa: Elsevier Churchill Livingstone; 2009:chap279.

Montoya JG. Toxoplasmosis. In: Goldman L, Schafer AI, eds. Cecil Medicine. 24th ed. Philadelphia, Pa: Saunders Elsevier; 2011:chap 357.


Review Date: 10/6/2012
Reviewed By: David C. Dugdale, III, MD, Professor of Medicine, Division of General Medicine, Department of Medicine, University of Washington School of Medicine. Jatin M. Vyas, MD, PhD, Assistant Professor in Medicine, Harvard Medical School; Assistant in Medicine, Division of Infectious Disease, Department of Medicine, Massachusetts General Hospital. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M. Health Solutions, Ebix, Inc.
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