Toxoplasma gondii IgG Avidity

The intended use of this test is to determine the avidity of the Toxoplasma IgG antibody in patients known to be positive for the Toxoplasma IgG antibody.

IgG avidity testing is used to support the diagnosis of recent primary Toxoplasma gondii infection during pregnancy. Maternal infections by Toxoplasma can cause severe complications to the fetus or congenital abnormalities. As a rule, the risk of maternal transmission is critically related to the time of infection; hence, it is important to determine the timing of infection in pregnant individuals. Toxoplasma gondii can cause central nervous system damage in the fetus and can lead to long-term sequelae, including sensorineural hearing loss and chorioretinitis, respectively. Since the risk to the fetus is critically related to the time of infection, it is essential to accurately determine whether a pregnant person has acquired a primary infection of T. gondii during gestation or earlier.

IgG avidity assays measure the binding strength between IgG antibodies and pathogen that can help distinguish a primary infection from a past infection. Following primary Toxoplasma infection, IgG antibodies have low binding strength (low avidity) then over 2-4 months mature to high binding strength (high avidity).