An enzyme-linked immunosorbent assay for detection of IgM antibodies to Toxoplasma gondii: use for diagnosis of acute acquired toxoplasmosis

In an enzyme-linked immunosorbent assay (ELISA) for detection of IgM antibodies to Toxoplasma gondii, sera from individuals with negative results in the Sabin-Feldman dye test (DT) and sera from individuals with chronic toxoplasma infection all yielded negative.results, even when tested undiluted. In contrast, of sera obtained from individ-uals with recently acquired toxoplasmosis, all sera that gave positive results in both the DT and the IgM-immunofluorescent antibody (lgM-IFA) test and 92.8 % of sera that gave negative results in the IgM-IFA test yielded strongly positive results in the IgM-ELISA. Thus, the IgM-ELISA is more sensitive than the IgM-IFA test in the diagnosis of recently acquired infection with T. gondii. Moreover, sera that gave negative results in the DT but that contained either antinuclear antibodies or rheumatoid factor and thus caused false-positive results in the IgM-IFA test all yielded negative results in the IgM-ELISA, probably because serum IgM and IgO fractions were separated during the initial step. Despite its proven value for the diagnosis of acute acquired toxoplasmosis [1-5], the toxoplasm