Toxoplasma blood test

Definition

The toxoplasma blood test looks for antibodies in the blood to a parasite called Toxoplasma gondii.

Alternative Names

Toxoplasma serology; Toxoplasma antibody titer

How the Test is Performed

A blood sample is needed.

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, some people may feel moderate pain. Others feel only a prick or stinging. Afterward, there may be some throbbing or a slight bruise. This soon goes away.

Why the Test is Performed

The test is done when the health care provider suspects that you have toxoplasmosis. The infection is a danger to a developing baby if a pregnant woman gets infected. It is also dangerous in people with HIV/AIDS.

In pregnant women, the test is done to:

• Check if a woman has a current infection or had an infection in the past.
• Check if the baby has the infection.

The presence of antibodies before pregnancy probably protects a developing baby against toxoplasmosis at birth. But antibodies that develop during pregnancy may mean the mother and baby have a current infection. This infection during pregnancy increases the risk for miscarriage or birth defects.

This test may also be done if you have:

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

Normal Results

Normal results mean you have likely never had a toxoplasma infection.

Normal value ranges may vary slightly among different laboratories. Some labs use different measurements or test different samples. Talk to your provider about the meaning of your specific test result.

What Abnormal Results Mean

Abnormal results mean that you have probably been infected with the parasite. Two types of antibodies are measured, IgM and IgG:

• If the level of IgM antibodies is raised, you likely became infected in the recent past (or currently).
• If the level of IgG antibodies is raised, you became infected sometime in the past.

Risks

There is little risk involved with having your blood taken. Veins and arteries vary in size from one person to another and from one side of the body to the other. Taking blood 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 lightheaded
• Multiple punctures to locate veins
• Hematoma (blood accumulating under the skin)
• Infection (a slight risk any time the skin is broken)

References

Mathison BA, Pritt BS. Medical parasitology. In: McPherson RA, Pincus MR, eds. Henry's Clinical Diagnosis and Management by Laboratory Methods. 24th ed. Philadelphia, PA: Elsevier; 2022:chap 65.

Montoya JG, Boothroyd JC, Kovacs JA. Toxoplasma gondii. In: Bennett JE, Dolin R, Blaser MJ, eds. Mandell, Douglas, and Bennett's Principles and Practice of Infectious Diseases. 9th ed. Philadelphia, PA: Elsevier; 2020:chap 278.