Evaluation of an enzyme-linked immunosorbent assay specific for human immunoglobulin G as a Screening test for detecting anti-toxoplasma antibodies

An evaluation of the enzyme-linked immunosorbent assay (ELISA) as a screening test for immunoglobulin G class-specific anti-Toxoplasma antibodies was conducted. Results for 191 serum specimens assayed by the ELISA, indirect hemagglutination (IHA), and methylene blue dye tests indicated that good qualitative agreement exists among these tests. High ELISA titers relative to methylene blue dye titers may be attributed in part to the presence of rheumatoid factor. ELISA results were found to be reproducible. A parallel study of 1,760 sera assayed by ELISA and IHA was performed with 3.0-mm-diameter serum filter paper spots as a source of specimen. When a 1:64 titer and 40 IU were used as threshold values for IHA and the ELISA, respectively, 4.8% of the specimens tested were positive in both tests. An additional 2% of these specimens were ELISA positive and IHA negative, whereas 2% were ELISA negative and IHA positive. The total number of positive specimens by either test (7%) closely agreed with previously reported results. In view of these data, the simplicity of the test, and relative economic considerations, the ELISA may be considered an alternative method for screening for anti-Toxoplasma antibodies.