What does a reactive hepatitis A, AB total result indicate?

Interpretation of Reactive Hepatitis A, AB Total Test Result

A reactive hepatitis A, AB total test indicates prior exposure to hepatitis A virus (HAV) with resulting immunity, meaning the person has recovered from a past HAV infection and is protected against future infection. 1

Understanding Hepatitis A Serology

Hepatitis A serologic testing includes two main antibody tests:

1. Hepatitis A IgM antibody: Indicates acute or recent infection (within the past 6 months)
2. Hepatitis A total antibody (AB total): Detects both IgM and IgG antibodies

When interpreting these results:

• Reactive AB total with negative IgM: Indicates resolved past infection with resulting immunity
• Reactive AB total with reactive IgM: Indicates acute or recent HAV infection
• Negative AB total: Indicates no prior exposure or immunity to HAV

Clinical Significance of Reactive HAV AB Total

A reactive hepatitis A total antibody test has several important clinical implications:

• Confirms immunity: The person has protective antibodies against future HAV infection 1
• Not infectious: The person is not currently infectious to others (unless IgM is also positive)
• No treatment needed: No specific treatment is required for past HAV infection 2
• No vaccination needed: HAV vaccination is unnecessary as natural immunity is already present 1

Differentiating Natural Immunity from Vaccine-Induced Immunity

To distinguish between natural immunity and vaccine-induced immunity:

• Natural immunity (past infection): Positive HAV AB total AND positive hepatitis A core antibody
• Vaccine-induced immunity: Positive HAV AB total WITHOUT positive hepatitis A core antibody 3

Important Considerations

• False positives: Low-level reactive results can occasionally occur without true HAV infection, especially in patients with other liver diseases 4, 5
• Early acute infection: In rare cases, early acute HAV infection can show reactive total antibody with non-reactive IgM due to assay sensitivity differences 6
• Chronic liver disease: Patients with chronic liver disease who have reactive HAV AB total are protected against HAV superinfection, which could otherwise cause severe complications 7

Recommended Follow-up Actions

1. Documentation: Record HAV immunity status in the patient's medical record
2. Patient education: Inform the patient they have recovered from a past HAV infection and are now immune
3. Consider other hepatitis testing: If not already done, consider testing for hepatitis B and C
4. No further HAV testing needed: Repeat testing for HAV is unnecessary as immunity is lifelong 3

Clinical Pitfalls to Avoid

• Don't confuse with active infection: A reactive AB total alone does not indicate current infection
• Don't recommend vaccination: HAV vaccination is unnecessary for those with natural immunity
• Don't ignore other liver disease: If liver enzymes are elevated, investigate other causes as past HAV infection doesn't cause chronic liver disease
• Don't miss early acute infection: If clinical suspicion for acute HAV is high despite negative IgM, consider repeat testing in 3-7 days 6, 5

Remember that hepatitis A is an acute, self-limiting infection that does not progress to chronic disease, unlike hepatitis B and C. A reactive HAV AB total test simply confirms past exposure and resulting immunity.