Evaluation of different measles IgG assays based on recombinant proteins using a panel of low-titre sera

During the WHO campaign to eradicate measles, accurate discrimination betwe en immune and non-immune individuals will become increasingly important. Du e to waning immunity in vaccinated populations, the performance of a measle s Ige assay depends mainly on its ability to detect reliably seronegative i ndividuals among many vaccinees with low antibody levels. New serological t ests based on recombinant proteins detect only a fraction of the total meas les virus (MV) specific antibodies. Therefore, several assays based on reco mbinant MV-haemagglutinin (ELISA and flow cytometry) or MV-fusion protein ( flow cytometry) as well as neutralisation and haemagglutination test have b een evaluated using a large panel of low-titre and negative sera. Since suc h an evaluation is highly dependent on threshold values for positivity, the receiver operating characteristic curve analysis was applied. The H-FACS a nd the H-ELISA showed the best performing characteristics (specificity: 97. 4 and 96.1%, respectively; sensitivity: 88.1 and 89.6%, respectively) and m ay be an alternative to the neutralisation assay. The number of undefined/g rey zone sera was significantly lower compared to a commercial whole virus- based ELISA and therefore fewer individuals would be vaccinated unnecessari ly. (C) 2000 Elsevier Science B.V. All rights reserved.