Evaluation of two novel enzyme immunoassays using recombinant antigens to detect cytomegalovirus-specific immunoglobulin M in sera from pregnant women

Background: Two novel enzyme linked immunosorbent assays (ELISA) (Abbott IM x CMV IgM 2.0, and Cobas Core CMV IgM EIA recomb, research version) which u se recombinant antigens to detect cytomegalovirus (CMV)specific IgM antibod ies were evaluated. Objectives: A new ELISA is normally evaluated against a gold standard comme rcial kit, which in this case does not exist. We therefore evaluated the tw o novel recombinant ELISA against four conventional ELISAs and a recently d eveloped CMV IgM immunoblot containing four purified viral and four recombi nant proteins. Study design: A total of 280 sera from pregnant women and 42 potentially cr oss-reactive sera were investigated using the six ELISAs, including 101 ser a which were also tested using the new IgM immunoblot. Results: Relative sensitivity, relative specificity and overall agreement d iffered according to the reference assay. The Cobas Core CMV EIA recomb sho wed much higher agreement with the ELISA consensus, and the IMx CMV IgM 2.0 with the immunoblot. Conclusion: The evaluation of these new IgM assays in terms of their agreem ent with either commercial ELISA kits or the IgM immunoblot demonstrates th at the question 'which reference method?' is still open. However the recomb inant IgM assays may improve the diagnosis of CMV infection in pregnancy si nce the recombinant technology offers helpful tools for identifying diagnos tically relevant proteins and allows the use of standardized pure Preparati ons of antigens. For serological diagnosis of CMV infection in pregnancy tw o IgM assays that can be relied upon should be performed. IgM positive sera should be tested with supplementary assays to differentiate primary from n on-primary infection. (C) 1999 Elsevier Science B.V. All rights reserved.