What does a Hepatitis A Antibody (Ab) total reactive result mean?

Interpretation of Hepatitis A Antibody (Ab) Total Reactive Result

A positive (reactive) Hepatitis A total antibody test indicates immunity to Hepatitis A virus (HAV) infection, either from previous natural infection or vaccination. 1

Detailed Interpretation

• A positive test for total anti-HAV indicates immunity to HAV infection but does not differentiate current from previous HAV infection or vaccination-induced immunity 1
• The presence of total anti-HAV (which includes both IgM and IgG antibodies) indicates that the person has been exposed to HAV at some point in their life, either through natural infection or vaccination 1
• Antibody produced in response to HAV infection persists for life and confers protection against reinfection 1

Clinical Significance

• To determine if this represents a current/recent infection versus past infection or vaccination, testing for IgM anti-HAV would be necessary 1
• If IgM anti-HAV is positive, this would indicate acute or recent HAV infection (typically within the past 6 months) 1
• If IgM anti-HAV is negative, this would indicate either:
  • Past HAV infection with natural immunity 1
  • Immunity from HAV vaccination 1

Important Considerations

• The anti-HAV tests might be positive after hepatitis A vaccination, although they are usually not sensitive enough to detect the low level of protective antibody after vaccination 1
• In some early acute hepatitis A cases, anti-HAV IgM may be non-reactive while anti-HAV total is reactive due to assay sensitivity differences 2
• Protective antibody levels from natural infection have been shown to persist for life 1
• After vaccination, protective antibody levels persist for at least 20-40 years according to kinetic models 1

Clinical Applications

• No further HAV vaccination is needed for individuals with positive total anti-HAV, as they already have immunity 1
• No specific treatment or follow-up is typically required for individuals with positive total anti-HAV and negative IgM anti-HAV (indicating past infection or vaccination) 1
• For individuals with positive total anti-HAV who are being evaluated for acute hepatitis, testing for other causes of hepatitis should be considered if IgM anti-HAV is negative 1

Potential Pitfalls

• Do not confuse HAV antibody testing with HBV (Hepatitis B) antibody testing, which has different interpretation patterns 1
• False-positive IgM anti-HAV test results can occur, particularly in asymptomatic persons with low pretest probability of acute HAV infection 3
• The total anti-HAV assay may have higher sensitivity in detecting IgM antibodies than specific anti-HAV IgM assays in early infection 2