What to do with a reactive anti-HAV (Hepatitis A Virus) IgG (Immunoglobulin G) result?

Management of Reactive Anti-HAV IgG

A reactive anti-HAV IgG result indicates immunity to hepatitis A from either past infection or vaccination, requires no treatment or follow-up testing, and provides lifelong protection against future hepatitis A infection. 1

Interpretation of the Result

The presence of anti-HAV IgG (or total anti-HAV) signifies past exposure to hepatitis A virus through either natural infection or vaccination, and this antibody persists for life conferring complete protection against reinfection. 1, 2

• Protective antibody levels from natural infection persist for life 2
• After vaccination, protective antibody levels persist for at least 20-40 years according to kinetic models 2
• A positive total anti-HAV test does not differentiate between immunity from past infection versus vaccination 2

Determining Acute vs. Past Infection

If there is clinical concern about distinguishing current from past infection, additional testing may clarify the timeline 2:

• IgM anti-HAV positive = acute or recent infection (typically within past 6 months) 1, 2
• IgM anti-HAV negative with IgG positive = past infection with natural immunity or immunity from vaccination 2
• IgM typically becomes detectable 5-10 days before symptom onset and declines to undetectable levels within 6 months after infection 3, 2

Important Diagnostic Pitfall

False-positive HAV IgM results can occur due to low positive predictive value in populations with low hepatitis A prevalence, and can be triggered by other viral infections including infectious mononucleosis, cytomegalovirus, and parvovirus. 3

• In elderly patients or those with polyclonal immune stimulation, IgM may be falsely positive despite no acute HAV infection 4, 5
• IgG avidity testing (when available) can distinguish true acute infection (low avidity <50%) from immune reactivation or false-positive IgM (high avidity >70%) 4, 5
• Some early acute hepatitis A patients may show anti-HAV IgM non-reactive but total anti-HAV reactive results due to assay sensitivity differences 6

Clinical Management

No treatment or follow-up testing is necessary for an isolated positive anti-HAV IgG result without symptoms. 1

• No further hepatitis A vaccination is needed, as the patient already has immunity 2
• The patient is protected against future hepatitis A infection 1
• For individuals with chronic liver disease, having hepatitis A antibodies is beneficial as it protects against additional liver damage that could occur with acute hepatitis A infection 1

Special Populations

Immunocompromised individuals should discuss this result with their healthcare provider, as antibody protection may wane more quickly in this population. 1

• For persons with HIV infection, antibody response can be directly related to CD4+ T-cell levels 7
• Although persons with HIV who have lower CD4+ counts may have weaker responses to vaccination, the presence of anti-HAV IgG still indicates current immunity 7

Family and Household Considerations

Family members and household contacts who haven't had hepatitis A or been vaccinated should consider getting the hepatitis A vaccine, especially those with chronic liver conditions. 1

• Hepatitis A is transmitted through the fecal-oral route via contaminated food or water and close person-to-person contact 1
• Secondary attack rates of 15-30% have been reported in households without postexposure prophylaxis 7