Toxoplasma test

Definition

A toxoplasma test checks for the presence of antibodies to toxoplasma in the blood.

How the test is performed

Blood is drawn from a vein, usually from the inside of the elbow or the back of the hand. The puncture site is cleaned with antiseptic. An elastic band is placed around the upper arm to apply pressure and cause the vein to swell with blood.

A needle is inserted into the vein, and the blood is collected in an air-tight vial or a syringe. During the procedure, the band is removed to restore circulation. Once the blood has been collected, the needle is removed, and the puncture site is covered to stop any bleeding.

For infants or young children, the area is cleansed with antiseptic and punctured with a sharp needle or a lancet. The blood may be collected in a pipette (small glass tube), on a slide, onto a test strip, or into a small container. A bandage may be applied to the puncture site if there is any bleeding.

Antibodies are detected by multiple tests, including an indirect fluorescent antibody test, an 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 performed to detect toxoplasmosis at birth or shortly after. It may also screen pregnant women for the antibodies to toxoplasma. The presence of antibodies before pregnancy probably protects a fetus against toxoplasmosis at birth (congenital). Antibodies developed during pregnancy may mean possible infection of the baby, with an increased risk of miscarriage or birth defects.

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.

What abnormal results mean

A titer of 1:16 - 1:256 indicates a probable previous infection. A titer of greater than 1:1,024 may indicate an active toxoplasmosis infection.

What the risks are

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

Special considerations

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.

Illustrations

Blood test

Page Content:

Toxoplasma serology; Toxoplasma antibody titer