[Toxoplasmosis IgG avidity: what importance does it have in pregnancy?]

Avidity describes the binding strength of specific antibody to antigen. It was found to be low in the first phase after primary infection but then to increase over time. In addition to classic serodiagnosis of toxoplasmosis, measurement of avidity provides information making it possible to distinguish between acute and chronic infection and is of particular interest in pregnant women. In 229 women we found IgG and IgM antibodies suggestive of acute infection. A total of 188 (82%) had an avidity index > 0.3, indicating that the infection had occurred at least four months earlier. Based on this additional information, repeated testing and unnecessary anxiety can be avoided.