Reproducible enzyme-linked immunosorbent assay with a magnetic processing system for diagnosis of toxoplasmosis.

An enzyme-linked immunosorbent assay with polycarbonate-coated iron beads as the solid phase and with magnetic processing devices was evaluated for the quantitation of antibodies to Toxoplasma gondii in human serum samples. Under the parameters and other basic conditions determined in this study, the assay was highly reproducible: coefficients of variation for the absorbance values obtained with the positive serum were 2.42% in same-day tests and 3.75% in day-to-day tests. Significant correlations were observed between the present assay system and other conventional serological tests: correlation coefficients were 0.960 with the dye test and 0.929 with the latex agglutination test. Statistical analysis based on the frequency distribution of absorbance values for dye-test-positive and dye-test-negative serum samples gave feasible border lines for distinguishing between positive and doubtful samples (0.357) and between doubtful and negative samples (0.266). Under this diagnostic criterion, the results of our assay system agreed remarkably well with those obtained by the dye test and the latex agglutination test, with consistencies of 94.9 and 93.9%, respectively.