Validation of an anti-measles virus-specific IgG assay with oral fluid samples for immunization surveillance in Bangladesh

Immune marker surveys may be used as substitutes or in conjunction with traditional surveys to monitor immunization program performance. This study assessed the validity and reliability of the Microimmune anti-measles virus-specific IgG ELISA with oral fluid samples (OF-ELISA) among a random sample of children ages 12-16 months in Bangladesh. Up to two oral fluid samples and one serum sample were analyzed for the presence of protective levels of anti-measles IgG antibodies. Results from the OF-ELISA were compared to the Enzygnost anti-measles IgG ELISA with serum and multivariate logistic regression models were developed to identify risk factors for false negative oral fluid results. Anti-measles IgG antibodies were measured in 330 paired oral fluid and serum samples. Immune marker prevalence of measles IgG antibodies was significantly higher in serum (88.1%, 95% CI: [84.1, 91.5]) than oral fluid (56.1% [50.2, 61.5]). Sensitivity (60.2% [54.1, 66.0]) and specificity (75.7% [58.8, 88.2]) of the OF-ELISA were lower than expected, but sensitivity significantly improved for individuals with higher anti-measles IgG in serum. False negative oral fluid results were associated with month of sample collection and variability between data collectors and assay procedures. Due to poor performance, caution should be exercised when using oral fluid samples to assess population immunity to measles virus, especially in highly vaccinated populations.