Prospective study of IgM to Toxoplasma gondii on Beekman Coulter's Access (TM) immunoassay system and comparison with Zeus ELISA and Gull IFA assays

We compared a new assay for Toxoplasma IgM on the Access(TM) analyzer (Beck man Coulter, Inc., Chaska, MN, USA), a random access instrument based on th e principle of paramagnetic particle enzyme immunoassay with an enzyme-link ed immunosorbent assay (ELISA) (Zeus Scientific, Inc., Raritan, NJ, USA) an d an immunofluorescent assay (IFA) (Gull Laboratories, Inc., Salt Lake City , UT, USA). Four hundred fresh, unfrozen clinical samples from pregnant wom en (n = 154), HIV positive patients (n = 41), and patients in whom infectio n with Toxoplasma gondii was suspected (n = 200) were collected and assayed over a three month period. The specificity of the Access assay was compare d to the consensus results. Results that were discrepant between the ELISA and IFA were resolved using a third IFA (Zeus). Once resolved, the specific ity for the Access assay, the Zeus ELISA and the Gull IFA were 99.22%, 97.9 1%, and 99.45%, respectively. We conclude that the Access assay specificity is comparable to consensus results, minimizing false positive results; and because it is a random access instrument, it may be preferable over batch methods. (C) 2000 Elsevier Science Inc. All rights reserved.