Congenital toxoplasmosis-False is:
Serological tests in Congenital Toxoplasmosis: Assay Characteristics IgG Appears in 1-2 weeks, peaks at 1-2 months & persists throughout life; Transplacental IgG disappears by 6-12 m age; But presence of IgG in the serum does not confirm the diagnosis because IgG can easily cross the placenta IgA It rises rapidly & usually disappears by 7 months; IgA has greater sensitivity for neonates compared to IgM assays; So IgA ELISA is better than IgM IgM IgM appears within 2 weeks, peaks at 1 month & disappears by 6-9 months. Because IgM does not cross the placenta, it is the test of choice for determining congenital infection Avidity Test It measures the strength of antigen antibody reaction, which increases with duration of infection . High avidity test - Infection began > 16 weeks earlier; Low avidity test - Indicates recent infection.
Diagnosed by detection of IgM in cord blood
IgA is more sensitive than IgM for detection
Dye test is gold standard for lgG
Avidity testing must be done to differentiate IgA & IgM
Congenital Infections