Performance of IgG and IgM Enzyme-Linked Immunosorbent Assays for Detection of West Nile Virus-Specific Antibodies

Strategic Insights -

Scientists have developed and assessed the performance of IgG and IgM enzyme-linked immunosorbent assays (ELISAs) using a West Nile virus (WNV) recombinant antigen for the detection of WNV- and other flavivirus-specific antibodies. The assays were developed by Focus Technologies and evaluated using serum panels from normal and diseased individuals. The results showed that the IgG ELISA had a sensitivity of 97.6% and a specificity of 92.1%, while the IgM ELISA had a sensitivity and specificity of 99.3% and 100%, respectively. The IgM ELISA showed lower cross-reactivity with flavivirus sera compared to the IgG ELISA.

Key Takeaways:

  • The Focus Technologies IgG ELISA had a sensitivity of 97.6% and a specificity of 92.1% (excluding non-WNV flavivirus sera).
  • The comparative method for WNV IgG may lack sensitivity in detecting IgG in early WNV infection, which may make the specificity of the Focus IgG ELISA higher than 92.1%.
  • The Focus Technologies IgM ELISA had a sensitivity and specificity of 99.3% (excluding the non-WNV flavivirus sera).
  • The overall cross-reactivity for the IgM ELISA to flavivirus sera was 12%.
  • The use of a background subtraction method for the IgM ELISA eliminated all 15 false-positive results, giving a specificity of 100% for the Focus IgM ELISA.
  • In a selected population of 706 sera, 15 false-positive WNV IgM sera were identified.
  • The IgM ELISA showed lower cross-reactivity with flavivirus sera compared to the IgG ELISA.

Statistics:

  • 807 sera were used to assess the IgG ELISA kit
  • 1,423 sera were used to assess the IgM ELISA kit
  • 97.6% sensitivity and 92.1% specificity for the IgG ELISA (excluding non-WNV flavivirus sera)
  • 99.3% sensitivity and 100% specificity for the IgM ELISA (excluding non-WNV flavivirus sera)
  • 12% overall cross-reactivity for the IgM ELISA to flavivirus sera
  • 31% of St. Louis encephalitis patients were found to be WNV IgM positive
  • No yellow fever vaccinees were found to be WNV IgM positive
  • 15 false-positive WNV IgM sera were identified in a selected population of 706 sera

Sources:

  • Hogrefe, W. R., et al. (2004). Performance of immunoglobulin G (IgG) and IgM enzyme-linked immunosorbent assays using a West Nile virus recombinant antigen (PreM/E) for detection of West Nile virus- and other flavivirus-specific antibodies. J Clin Microbiol, 42(10), 4641-4648.
  • American Society for Microbiology. (2004). Journal of Clinical Microbiology, 42(10), 4641-4648.