Sensitivities and specificities of ELISA to detect anti-A(H1N1)pdm09 HA IgM, IgG, and IgA antibodies in infected and unexposed personsa

IsotypeSensitivityb (%) for age group:Sensitivityc (%) for:Specificity (%) for age group:
≤5 yr (n = 19)6–15 yr (n = 11)16–80 yr (n = 39)Primary infection (n = 13)Nonprimary infection (n = 39)3–5 yr (n = 19)6–15 yr (n = 20)16–79 yr (n = 86)
  • a Assay sensitivities were based on antibody responses obtained in convalescent-phase sera from A(H1N1)pdm09-infected persons. All had MN antibody titers of ≥40 and HI antibody titers of ≥20 (Veguilla et al. [24]). Sera were grouped by age or by primary or nonprimary infections status determined as described in Materials and Methods. Individuals experiencing a primary infection were ≤5 years old, and those with nonprimary infections were >16 years old. Assay specificities were determined using sera from healthy age-matched individuals collected in 2007 and 2008 prior to the emergence of the A(H1N1)pdm09 virus. Seropositivity was based on an immunoglobulin concentration ratio of test serum sample to the concentration of the positive control, IS/09/194 (T/P ratio), that achieved at least 90% specificity for all age groups. The T/P ratio thresholds were 2.0, 0.4, and 0.6 for the IgM, IgG, and IgA responses, respectively.

  • b The sensitivity was determined in 3 age groups (≤5 years, 6–15 years, and 16–80 years).

  • c The sensitivity was determined in persons with primary infection and those with nonprimary infection.

  • d Statistically significant at a P value of <0.05.

  • e Statistically significant at a P value of <0.05.

  • f Statistically significant at a P value of <0.05.

  • g Statistically significant at a P value of <0.05.