VIDAS TOXO IgG Avidity assay to test for recent Toxoplasma gondii infection receives FDA clearance

U.S. Food and Drug AdministrationMay 20 2011

On May 18, the U.S. Food and Drug Administration cleared the first test to help determine whether a pregnant woman or a person with swollen lymph nodes testing positive for toxoplasmosis, sometimes known as cat scratch disease, developed the infection within the past four months.

Toxoplasmosis is caused by the parasite Toxoplasma gondii. The infection can cause serious health problems in people with compromised immune systems. Women who become infected just before or during pregnancy may pass the parasite on to their unborn child, resulting in miscarriage, stillbirth, or an abnormally small or large head. Infection can also lead to vision loss, mental disability, seizures or other health problems later in life for the child.

Cats are most often associated with the parasite, but many other species of animals and birds also serve as hosts. The parasite also is found in people worldwide. Common symptoms of toxoplasmosis include swollen lymph nodes and flu-like symptoms.

Toxoplasmosis is considered to be a leading cause of death attributed to foodborne illness, according to the Centers for Disease Control and Prevention. More than 60 million people in the United States may be infected with Toxoplasma gondii. The parasite may be transmitted to people when they eat raw, undercooked or contaminated meat or come in contact with infected cat feces or litter.

The VIDAS TOXO IgG Avidity assay can be used to rule out recent Toxoplasma gondii infection. The test works by detecting how strongly IgG avidity antibodies bind to the Toxoplasma gondii antigens in the assay. IgG avidity antibodies from infections older than four months bind tightly with the antigens, while IgG avidity antibodies from infections acquired in the past four months form weaker bonds.

"Toxoplasmosis can have serious and lasting health consequences for infants that acquire the infection in the womb," said Alberto Gutierrez, Ph.D., director of the Office of In Vitro Diagnostic Device Evaluation and Safety in FDA's Center for Devices and Radiological Health. "This test gives doctors an additional tool to determine if women with confirmed cases of toxoplasmosis acquired the infection before or during pregnancy."

The VIDAS TOXO IgG Avidity Assay test is for use in people who have been confirmed with the Toxoplasma gondii infection by using the VIDAS TOXO IgG II test and who are pregnant or have swollen lymph glands. The VIDAS TOXO IgG Avidity Assay test alone should not be used as a basis for clinical decisions.

The performance of the VIDAS TOXO IgG Avidity Assay has not been established for prenatal screening, for immunocompromised patients, or for cases of toxoplasmosis reinfection or relapse, and the FDA has not cleared or approved the VIDAS TOXO IgG Avidity Assay for blood or plasma donor screening.  

The VIDAS TOXO IgG Avidity assay is manufactured by bioMerieux Inc. of  Hazelwood, Mo.