Interpretation of Hepatitis A Antibody Total Reactive Result
A hepatitis A antibody (Ab) total reactive result indicates that a person has immunity to hepatitis A virus (HAV) infection, either from past natural infection or from vaccination. 1
What This Result Means
- A positive test for total anti-HAV indicates immunity to HAV infection but does not differentiate between current infection, previous infection, or vaccination-induced immunity 1
- The presence of total anti-HAV shows that the person has been exposed to HAV at some point in their life, either through natural infection or vaccination 1
- Antibodies produced in response to HAV infection persist for life and confer protection against reinfection 1
Clinical Significance
- To determine if a positive total anti-HAV result represents a current or past infection, testing for IgM anti-HAV would be necessary 1
- If IgM anti-HAV is positive, this indicates acute or recent HAV infection (typically within the past 6 months) 1
- If IgM anti-HAV is negative, this indicates either past HAV infection with natural immunity or immunity from HAV vaccination 1
Duration of Immunity
- Protective antibody levels from natural HAV 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
- No further HAV vaccination is needed for individuals with positive total anti-HAV, as they already have immunity 1
Important Considerations
- The anti-HAV total assay can detect both IgM and IgG antibodies to HAV 2
- In some cases, early acute hepatitis A infection may show anti-HAV IgM non-reactive but anti-HAV total reactive results due to differences in assay sensitivity 2
- For individuals being evaluated for acute hepatitis with positive total anti-HAV, testing for other causes of hepatitis should be considered if IgM anti-HAV is negative 1
Clinical Applications
- Very low levels of HAV antibody are sufficient to prevent infection, as demonstrated by the approximately 90% efficacy of immune globulin in preventing hepatitis A 3
- 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
- The presence of anti-HAV indicates that a person has been exposed to HAV and has developed protective immunity 1
Potential Pitfalls
- Do not confuse HAV antibody testing with HBV antibody testing, which has different interpretation patterns 1
- Some early acute hepatitis A patients may show anti-HAV IgM non-reactive but anti-HAV total reactive results due to assay sensitivity differences 2
- Antibody titers after vaccination (GMT of 3,400 mIU/mL) are typically lower than those after natural infection (GMT of 15,400 mIU/mL), but both provide protective immunity 4