Agreement between ELISA and plaque reduction neutralisation assay in Detection of respiratory syncytial virus specific antibodies in a birth Cohort from Kilifi, coastal Kenya.

Background: Severe disease associated with respiratory syncytial virus (RSV) infection occurs predominantly among infants under 6 months of age. Vaccines for prevention are in clinical development. Assessment of the vaccine effectiveness in large epidemiological studies requires serological assays which are rapid, economical and standardised between laboratories. The objective of this study was to assess the agreement between two enzyme linked immunosorbent assays (ELISA) and the plaque reduction neutralisation test (PRNT) in quantifying RSV specific antibodies. Methods: Archived sera from 99 participants of the Kilifi Birth Cohort (KBC) study (conducted 2002-2007) were screened for RSV antibodies using 3 methods: ELISA using crude RSV lysate as antigen, a commercial RSV immunoglobulin G (IgG) ELISA kit from IBL International GmbH, and PRNT. Pearson correlation, Bland-Altman plots and regression methods were used in analysis. Results: There was high positive correlation between the IBL RSV IgG ELISA and PRNT antibodies (Pearson r=0.75), and moderate positive correlation between the crude RSV lysate IgG ELISA and PRNT antibodies (r= 0.61). Crude RSV lysate IgG ELISA showed a wider 95% limit of agreement (-1.866, 6.157) with PRNT compared to the IBL RSV IgG ELISA (1.392, 7.595). Mean PRNT titres were estimated within a width of 4.8 log (2)PRNT and 5.6 log (2)PRNT at 95% prediction interval by IBL RSV IgG and crude RSV lysate IgG ELISA, respectively. Conclusion: Although, the IBL RSV IgG ELISA is observed to provide a reasonable correlate for PRNT assay in detecting RSV specific antibodies, it does not provide an accurate prediction for neutralizing antibody levels. An RSV neutralising antibody level is likely to fall within 2.4 fold higher and 2.4 fold lower than the true value if IBL RSV IgG ELISA is used to replace PRNT assay. The utility of an ELISA assay in vaccine studies should be assessed independent of the PRNT method.