Comparison of two commercial ELISA kits for detection of rubella specific IgM and IgG antibodies

Abstract Enzyme linked immunosorbent assay (ELISA) plays an important role in laboratory confirmation of congenital rubella syndrome (CRS), postnatal rubella and seroprevalence studies in different populations. Variation of results are documented for samples tested by different commercial kits. The Enzygnost rubella ELISA, widely used in the WHO network, is expensive and not readily available. In the present study, performance of the Euroimmun ELISA was compared to the Enzygnost ELISA for detection of rubella specific IgM and IgG antibodies. Two hundred and eighty five serum samples collected from suspected CRS patients identified through a recently initiated surveillance for CRS at six sentinel hospitals and 435 serum samples from a serosurvey of pregnant women from these sites, were available for testing of rubella specific IgM and IgG antibodies respectively. Qualitative agreement (concordance percentage and Cohen’s Kappa coefficient -κ) was evaluated for both IgM and IgG assays. Bland – Altman plots were used to assess the difference in quantitative agreement for IgG titers. Good qualitative agreement between the two ELISA kits was observed for detection of both anti rubella IgM (94.7% agreement and k of 0.86) and IgG (96.3% agreement and k of 0.84). Sensitivity and specificity of Euroimmun assays compared to Enzygnost was 100% and 93.1% for IgM and 95.9% and 100% for IgG respectively. Bland – Altman analysis for paired quantitative results of rubella specific IgG yielded a mean difference of 0.781 IU/ml with majority of values (97.1%) within ± 2 SD of the mean difference. Euroimmun ELISA provided on an average, higher titers as compared to Enzygnost. Our study findings suggest that Euroimmun ELISA may be considered for detection of rubella specific IgM in suspected CRS cases and rubella specific IgG in surveillance studies.