DIAGNOSTIC IMPLICATIONS OF KINETICS OF IMMUNOGLOBULIN-M AND IMMUNOGLOBULIN-A ANTIBODY-RESPONSES TO TOXOPLASMA-GONDII

We evaluated immunoglobulin M (IgM) and IgA assays that could improve the predictive value for recently acquired toxoplasma infection for pa tients with positive screening test results, Follow-up sera were colle cted from 82 patients whose initial serum specimen had a reactive anti -Toxoplasma gondii IgM result. According to the evolution of the immun e response, patients were divided retrospectively into two groups: one in which a recent infection was unlikely and the other one with an ev olving immune response suggestive of recent toxoplasma infection. All IgM and one of three IgA assays used in the study are suitable for scr eening pregnant patients, with a negative predictive value of 100%. Th e predictive value of positive results is much lower because of the lo w prevalence of acute toxoplasmosis in pregnant women and the long per sistence of IgM after acute infection. In the present study, all excep t one IgM enzyme immunoassay remained positive well beyond 6 months af ter the initial sample was tested. The IgM immunofluorescence test had the shortest persistence of positivity in most cases. IgA tests were either too insensitive or remained reactive too long to be useful for screening pregnant patients, Interpreting enzyme immunoassays with mod ified cutoff values and the combination of two tests could improve the predictive value of positive results to about 80% in terms of recent infection.