Antibody Test Excludes Recent Toxoplasmosis Infection

The test, which measure immunoglobulin G (IgG) response to the parasite Toxoplasma gondii, can also be used for a person with swollen lymph nodes who had tested positive for toxoplasmosis.

The VIDAS TOXO IgG Avidity assay can be used to rule out recent T. gondii infection. The test works by detecting how strongly IgG avidity antibodies bind to the T. gondii antigens in the assay. The 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.

The VIDAS TOXO IgG Avidity Assay test (bioMérieux, Inc.; Hazelwood, MO, USA) is for use in people who have been confirmed with the toxoplasmosis 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. Although cleared by the US Food and Drug Administration, (FDA, Silver Springs, MD, USA), for determining when the infection occurred, the FDA has not cleared or approved the VIDAS TOXO IgG Avidity Assay for blood or plasma donor screening.

Alberto Gutierrez, PhD, a director at the FDA, said, "Toxoplasmosis can have serious and lasting health consequences for infants that acquire the infection in the womb. This test gives doctors an additional tool to determine if women with confirmed cases of toxoplasmosis acquired the infection before or during pregnancy." A common symptom of toxoplasmosis includes swollen lymph nodes and flu-like symptoms and it is found in people worldwide. 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.

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BioMérieux Inc.
US Food and Drug Administration