What does the presence of IgG antibodies to EBV (Epstein-Barr Virus) viral capsid antigen indicate?

EBV Viral Capsid Antigen IgG Antibody Interpretation

The presence of IgG antibodies to Epstein-Barr virus (EBV) viral capsid antigen (VCA) indicates past exposure to EBV infection, with the specific interpretation depending on the pattern of other EBV serological markers. 1

Interpretation of EBV VCA IgG in Different Serological Patterns

The interpretation of EBV VCA IgG must be considered within the context of other EBV serological markers:

1. VCA IgM (+), VCA IgG (+), EBNA IgG (-):

   • Indicates acute primary infection within the past 6 weeks
   • This pattern represents the early antibody response to EBV infection 1

2. VCA IgM (-), VCA IgG (+), EBNA IgG (+):

   • Indicates past infection (>6 weeks ago)
   • This is the most common pattern in adults as approximately 90-95% of adults worldwide have been infected with EBV 1

3. VCA IgM (-), VCA IgG (-), EBNA IgG (-):

   • Indicates no previous EBV infection 1

Clinical Significance and Additional Testing

• IgG avidity testing can help distinguish between recent and past infection when serological patterns are ambiguous:

  • Low avidity VCA IgG suggests recent primary infection
  • High avidity VCA IgG suggests past infection or reactivation 1, 2

• VCA IgG antibodies typically appear within 4-7 days after symptom onset and persist for life, making them a reliable marker of EBV exposure 1

• Relying solely on VCA IgG is insufficient for determining the stage of EBV infection; a complete serological panel is recommended 1, 3

Common Pitfalls in Interpretation

• False interpretation of isolated VCA IgG positivity: A positive VCA IgG alone only indicates exposure to EBV at some point but cannot determine if the infection is acute, recent, or past 1

• Misinterpretation in immunocompromised patients: In these patients, serological patterns may be atypical, and VCA IgG positivity with IgM positivity may represent reactivation rather than primary infection 2, 4

• Overlooking the need for comprehensive testing: The Centers for Disease Control and Prevention recommends testing for VCA IgM, VCA IgG, and EBNA IgG as the standard diagnostic approach 1

Clinical Algorithm for EBV Serological Interpretation

1. Test for VCA IgM, VCA IgG, and EBNA IgG antibodies
2. Interpret the pattern according to the following:
   • If VCA IgG (+) and EBNA IgG (+): Past infection
   • If VCA IgM (+), VCA IgG (+), and EBNA IgG (-): Acute primary infection
   • If all markers negative: No previous EBV infection
3. For ambiguous results, consider:
   • IgG avidity testing
   • Quantitative EBV viral load by PCR if clinically indicated
   • Heterophile antibody testing (though this may miss ~10% of cases, especially in children under 10) 1

Special Considerations

• In transplant recipients, positive EBV VCA IgG before transplant indicates past infection and risk of reactivation 1

• In patients with indeterminate serology (equivocal IgM results), IgG avidity testing can help classify 83.3% as past infection, 10% as post-acute, and 6.7% as acute primary infection 2

• "Serological EBV reactivation" (positive IgM-EA and IgG-EBNA) may not always correlate with clinical manifestations and could reflect non-specific immune activation 4