Comparative and analytical study on active toxoplasmosis to assess the IgG avidity in correlation to serological profile in a cohort of Egyptian patients

Proper diagnosis of toxoplasmosis is very important for proper treatment in manifested cases and to prevent congenital toxoplasmosis in case of pregnancy. Screening of 180 pregnant females by automated immune assay for Toxoplasma IgG and IgM Abs was done first then positive cases and some of negative cases were evaluated for the Toxoplasma IgG avidity test versus Toxoplasma IgM and IgA Abs using ELISA technique for the detection of active toxoplasmosis during gestation using IHA rising titer as reference test. Assessment of Toxoplasma IgM by ELISA compared with rising titer of IHA as a reference test revealed that the sensitivity, specificity, PPV, and NPP of IgM by ELISA were 66.67, 88.73, 42.86, and 95.45%, respectively. Assessment of Toxoplasma IgA Abs by ELISA compared with rising titer IHA as a reference test showed that the sensitivity, specificity, PPV, and NPP of IgA Abs by ELISA were 44.4, 92.96, 44.4, and 92.96%, respectively. Additionally, by assessment of Toxoplasma IgG avidity compared with rising titer of IHA as a reference test, the sensitivity, specificity, PPV, and NPP of Toxoplasma IgG avidity were 100, 98.59, 90%, and 100%, respectively. Detection of specific Toxoplasma IgM antibodies by ELISA is not always sufficient in the diagnosis of early and late Toxoplasma gondii infection during pregnancy, because Toxoplasma-specific IgM antibodies may persist as long as 18 months after acute acquired infection. Thus, the specific IgG avidity test should be used as more or less low cost tool to detect acute toxoplasmosis.