A toxoplasmosis test is a blood test that checks for antibodies to the Toxoplasma gondii parasite. Your body's natural defense system (immune system) will make these antibodies only if you have been infected by this tiny parasite. The amount and type of antibodies you have shows whether your infection is recent or occurred in the past. More than one blood test may be done over several weeks.
For most people, toxoplasmosis isn't dangerous and goes away on its own. But if a pregnant woman becomes infected and passes it on to her growing baby (fetus), it can cause blindness and brain damage in the fetus.
You can be infected by eating food such as undercooked or raw meat from an infected animal or by handling an infected cat or its stool (feces). After you have been infected, you will have antibodies to Toxoplasma gondii.
Why It Is Done
A toxoplasmosis test is done to find out if a:
- Pregnant woman has antibodies from a toxoplasmosis infection.
- Baby has toxoplasmosis.
- Person with a weakened immune system, such as someone who has HIV, has a chance of getting a toxoplasmosis infection.
How To Prepare
In general, there's nothing you have to do before this test, unless your doctor tells you to.
How It Is Done
A health professional uses a needle to take a blood sample, usually from the arm.
How It Feels
When a blood sample is taken, you may feel nothing at all from the needle. Or you might feel a quick sting or pinch.
There is very little chance of having a problem from this test. When a blood sample is taken, a small bruise may form at the site.
Test results are usually ready in 1 to 3 days.
The results of the test are usually given in titers. A titer is a measure of how much the blood sample can be diluted with a saltwater solution (saline) before the antibodies can no longer be found.
Each lab has a different range for what's normal. Your lab report should show the range that your lab uses for each test. The normal range is just a guide. Your doctor will also look at your results based on your age, health, and other factors. A value that isn't in the normal range may still be normal for you.
Toxoplasmosis antibodies usually form within 2 weeks after a person is infected. The titer is the highest 1 to 2 months after infection.
- If high titers of the IgM type of antibody are found, it means the infection is recent. If high titers of the IgG type of antibody are present, it means an infection occurred in the past.
- Blood samples may be taken over several weeks to see if the number of antibodies is getting higher. This would mean the infection is recent.
- Low titers that do not get higher usually mean the infection occurred in the past. After you have had toxoplasmosis, you cannot be infected again.
Current as of: February 23, 2022
Author: Healthwise Staff
Sarah Marshall MD - Family Medicine
E. Gregory Thompson MD - Internal Medicine
Adam Husney MD - Family Medicine
Kathleen Romito MD - Family Medicine
Kirtly Jones MD - Obstetrics and Gynecology