Congenital toxoplasmosis - False is aEUR'
Avidity testing must be done to differentiate b/w IgA & Ig1VI Toxoplasma immunoglobulin pattern after acute infection IgG Appears within 1-2 weeks, peaks at 1-2 months and persists throughout life. But presence of IgG in the serum does not confirm the diagnosis because IgG can easily cross the placenta. - Thus IgG, in infant circulation may be of maternal origin or due to infection of the fetus. - Transplacental IgG antibody disappears by 6-12 months of age. IgM IgM appears within 2 weeks, peaks at 1 month and decline to undectable level within 6-9 months. Because IgM does not cross the placenta, it is the test of choice for determining congenital infectiondeg. IgA IgA rises rapidly and it usually disappears by 7 months. "IgA may have greater sensitivitydeg for neonates compared to 1gM assays". Serological tests to detect IgG + 4' Ilr Sabin7feldman dye IgGIFA test Differential agglutination Avidity test Test (IgG indirect (AC/HS) (IgG) (Most preferred Flourscent IgG test) antibody test It rises rapidly and does not persist as long as 1gM and IgA. Avidity test Measure .IgGdeg antibody It measures the strength of antigen antibody reactiondeg. - "This increases with duration of infection"a. High avidity requires at least 3 months to develop, thus helps to rule out acute infection: - High avidity test Infection began > 16 wks. - Low avidity test Indicates recent infection Panel of serological tests which are currently preferred over other tests for congenital Toxoplasmosis Sabin Feldman dye test (IgG) la ISAGA IgA ELISA (better than IgM ELISA) IgE ESAGA or ELISA Panel of serological tests for Maternal Toxoplasmosis Sabin Feldman dye test (IgG) IgM ISAGA IgM ELISA IgA ELISA IgE ISAGA or ELISA
Diagnosed by detection of IgM in cord blood
IgA is more sensitive than IgM for detection
Dye test is gold standard for IgG
Avidity testing must be done to differentiate between IgA & IgM