What does a reactive Epstein Barr Virus (EBV) Capsid Antibody (Ab) Immunoglobulin G (IgG) test result indicate?

What Does a Reactive EBV Capsid Antibody IgG Mean?

A reactive (positive) EBV VCA IgG result indicates that you have been infected with Epstein-Barr virus at some point in your life, but this single test result alone cannot distinguish whether the infection was recent or occurred years ago—you need additional antibody tests (VCA IgM and EBNA) to determine the timing of infection. 1

Understanding Your Test Result

Your positive VCA IgG means:

• You have been exposed to EBV - Over 90% of normal adults have IgG antibodies to VCA from past infection, so this is extremely common 2
• This antibody persists for life - VCA IgG develops rapidly during acute infection and remains detectable permanently 3
• Additional testing is essential - The presence of VCA IgG without knowing your VCA IgM and EBNA antibody status cannot distinguish between recent and remote infection 3

What You Need Next: The Complete EBV Antibody Panel

The Infectious Diseases Society of America explicitly recommends ordering a complete EBV-specific antibody panel including VCA IgM, VCA IgG, and EBNA antibodies to properly interpret your infection status 1, 3

Interpretation Based on Complete Panel Results:

• Recent primary infection (acute mononucleosis):

  • VCA IgM positive + VCA IgG positive + EBNA antibodies absent 1, 3
  • This pattern indicates infection within the past 1-2 months 3

• Past infection (most common scenario):

  • VCA IgG positive + EBNA antibodies present + VCA IgM negative 1, 3
  • EBNA antibodies develop 1-2 months after primary infection and persist for life 3
  • The presence of EBNA antibodies makes EBV unlikely as the cause of current acute symptoms 1, 2

• Possible reactivation (uncommon in immunocompetent patients):

  • VCA IgG positive + VCA IgM positive + EBNA antibodies present 4
  • This pattern is often due to non-specific immune activation rather than true EBV reactivation 5
  • In one study, 49% of patients with this pattern had false-positive IgM results from other causes 4

Special Considerations

If You Are Immunocompromised:

For transplant recipients, HIV-infected individuals, or those with congenital immunodeficiencies, the Infectious Diseases Society of America recommends quantitative EBV viral load testing by nucleic acid amplification (NAAT) rather than relying solely on serology 1, 2

• EBV DNA levels >10^2.5 copies/mg DNA in peripheral blood mononuclear cells indicate active infection 1, 2
• Increases in viral load may precede development of EBV-associated lymphoproliferative disease 2

If You Have Persistent Symptoms:

Chronic Active EBV Infection (CAEBV) should be suspected when you have markedly elevated VCA IgG (≥1:640) and EA IgG (≥1:160) with persistent infectious mononucleosis-like symptoms 6, 2

• CAEBV requires persistent or recurrent symptoms including fever, lymph node swelling, and hepatosplenomegaly 6
• Positive IgA antibodies to VCA and/or EA are often demonstrated in CAEBV 6, 2
• This diagnosis requires exclusion of other disease processes 6

Common Pitfalls to Avoid

• Do not assume VCA IgG alone means recent infection - This is the most common misinterpretation; you must have the complete panel 3
• Do not ignore false-positive VCA IgM results - IgM can be positive due to non-specific immune activation, reactivation, or cross-reactivity with other infections like CMV 5, 4
• Consider IgG avidity testing if timing is unclear - Low-avidity IgG indicates recent infection (within 6 months), while high-avidity indicates past infection (>6 months ago) 7, 8, 9

Bottom Line

Your positive VCA IgG confirms EBV exposure but requires VCA IgM and EBNA antibody testing to determine whether this represents a current infection requiring clinical attention or simply evidence of past exposure like the majority of adults. If you are immunocompromised or have persistent symptoms, viral load testing may be more appropriate than serology alone.