STUDY OF ABBOTT-TOXO-IMX SYSTEM FOR DETECTION OF IMMUNOGLOBULIN-G ANDIMMUNOGLOBULIN-M TOXOPLASMA ANTIBODIES - VALUE OF CONFIRMATORY TESTING FOR DIAGNOSIS OF ACUTE TOXOPLASMOSIS

We compared the Abbott Toro immunoglobulin G (IgG) and IgM IMx assays with the Sabin-Feldman dye test and an IgM enzyme-linked immunosorbent assay (ELISA) in 398 serum samples previously tested in our laborator y (retrospective group) and 1,000 consecutive serum samples, tested as they were received in our laboratory in 1995 (prospective group), In the retrospective group, the IgG IMx had a sensitivity of 100%, specif icity of 99.0%, positive predictive value of 99.0%, negative predictiv e value of 100%, and overall agreement of 99.5%. The percentages for t he IgM IMx were 97.8, 99.0, 98.9, 98, and 98.4%, respectively, In the prospective group, the IgG IMx had a sensitivity of 97.8%, specificity of 98.7%, positive predictive value of 97.8%, negative predictive val ue of 98.7%, and overall agreement of 98.4%, The percentages for the I gM IMx were 88.3, 95.9, 74.7, 98.3, and 95%. A serological profile (Ig A and IgE antibodies and the differential agglutination [AC/HS] test) was performed in an attempt to resolve discrepancies, Of 21 serum samp les that were positive in the IgM IMx and negative in the IgM ELISA, 1 9 had serological profiles which were most compatible with an infectio n acquired in the distant past, Of 8 serum samples which were positive in the IgM ELISA and negative in the IgM IMx, 5 had serological profi les which were most compatible with an infection acquired in the dista nt past, Of the 55 serum samples that were positive in both IgM tests, 21 were from patients who had serological profiles which were most co mpatible with an infection acquired in the distant past, In conclusion , our data highlight the importance of confirmatory testing for the di agnosis of recently acquired infection with Toxoplasma gondii. When co mpared with the dye test and IgM ELISA, the Toro Ige and IgM IMx assay s, respectively, revealed high overall agreement in the retrospective and prospective study.