<prompt> Congenital toxoplasmosis-False is-Diagnosed by detection of IgM in cord bloodIgA is more sensitive than IgM for detectionDye test is gold standard for IgGAvidity testing must be done to differentiate between IgA IgM  <response>: Ans. is d i.e., Avidity testing must be done to differentiate bw IgA IgM Avidity test is used to measure the strength of antigen-antibody reaction for IgG antibody not to differentiate betweenIgA IgM Toxoplasma immunoglobulins to diagnose congenital toxoplasmosis 1 IgG o Presence of IgG in infantss blood does not confirm the diagnosis of congenital toxoplasmosis because IgG can easily cross the placenta. So, one cannot predict whether the IgG is of maternal origin or due to fetal infection. o Transplacental IgG antibody disappears by 6-12 months of age. Serological tests to detect IgG : - i Sabin-Fieldman dye test Most preferred IgG test ii 1gG IFA test IgG indirect fluorscent antibody test iii Differential agglutination ACHS IgG test. iv Avidity test : - It measure the strength of antigen-antibody reaction for IgG antibody. 2 IgM o IgM does not cross the placenta; therefore, IgM is the test of choice for determining congenital infection. o Serological tests for IgM are : - i IgM IFA indirect fluorscent antibody test ii Double sandwich enzyme linked immunosorbant assay : - More sensitive than IgM IFA. iii immunosorbant agglutination assay ISAGA 3IgA o IgA may have greater sensitivity for neonate compared to IgM assay. o Serological tests for IgA are : - i Double sandwich enzyme linked immunosorbant assay IgA ELISA : - It is better than double sandwich IgM ELISA for diagnosis of congenital toxoplasmosis. The immunosorbant agglutination assay ISAGA IgA. 