Toxoplasma test

Alternative names
Toxoplasma serology; Toxoplasma antibody titer

This is a test to determine the presence of antibodies to toxoplasma in the blood.

How the test is performed

Blood is drawn from a vein, usually on the inside of the elbow or the back of the hand. The puncture site is cleaned with antiseptic, and an elastic band cuff is placed around the upper arm to apply pressure and restrict blood flow through the vein. This causes veins below the band to fill 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 an infant or young child, 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. Cotton or a bandage may be applied to the puncture site if there is any continued 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.

For infants and children:
The preparation you can provide for this test depends on your child’s age and experience. For specific information regarding how you can prepare your child, see the following topics:

How the test will feel
When the needle is inserted to draw blood, some people feel moderate pain, while others feel only a prick or stinging sensation. Afterward, there may be some throbbing.

Why the test is performed
The test is performed to detect congenital or postnatal toxoplasmosis or to screen pregnant women for the presence of antibodies to toxoplasma. The presence of antibodies before pregnancy probably protects a fetus against Congenital toxoplasmosis. Antibodies developed during pregnancy may indicate possible congenital infection with an increased risk of miscarriage or birth defects.

Normal Values
A titer 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 to 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.

Johns Hopkins patient information

Last revised: December 3, 2012
by Gevorg A. Poghosian, Ph.D.

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