What is the best way to assess a patient's immunity to hepatitis B?

Best Method for Assessing Hepatitis B Immunity

The best way to assess a patient's immunity to hepatitis B is through serologic testing for hepatitis B surface antibody (anti-HBs), with a level ≥10 mIU/mL indicating immunity. 1

Comprehensive Serologic Assessment

Initial Serologic Testing

• Testing for anti-HBs is the primary method to determine immunity to hepatitis B virus (HBV) infection 1
• A quantitative method that allows detection of the protective concentration of anti-HBs (≥10 mIU/mL) should be used, such as enzyme-linked immunosorbent assay (ELISA) 1
• Testing should be performed 1-2 months after completion of vaccination series to accurately assess immune response 1

Interpretation of Anti-HBs Results

• Anti-HBs ≥10 mIU/mL indicates protective immunity against HBV infection 1
• Immunocompetent persons with anti-HBs ≥10 mIU/mL after vaccination have long-term protection and do not need further periodic testing 1
• Anti-HBs <10 mIU/mL after vaccination indicates lack of protective immunity and need for revaccination 1

Distinguishing Source of Immunity

To fully understand a patient's HBV status and source of immunity, a more comprehensive panel is recommended:

Complete Serologic Panel

• HBsAg, anti-HBs, and total anti-HBc is the recommended panel to define a patient's HBV clinical status 1
• This combination helps distinguish between immunity from vaccination versus natural infection 1

Interpretation of Complete Panel Results

• Anti-HBs positive + anti-HBc negative: Immunity from vaccination 1
• Anti-HBs positive + anti-HBc positive: Immunity from resolved natural infection 1
• HBsAg positive: Active HBV infection (acute or chronic) 1
• Isolated anti-HBc positive (HBsAg negative, anti-HBs negative): May indicate previous infection with waning anti-HBs, false positive, or "occult" HBV infection 1

Special Considerations

High-Risk Populations

• For hemodialysis patients, annual testing of anti-HBs is recommended due to potential waning immunity 1
• Immunocompromised patients (HIV-infected persons, hematopoietic stem-cell transplant recipients, patients on chemotherapy) may need annual testing to assess anti-HBs concentrations 1
• Healthcare personnel should be tested for anti-HBs 1-2 months after vaccination to ensure protection in case of occupational exposure 1

Potential Pitfalls

• False positive HBsAg results can occur due to heterophilic antibody interference 2
• Passively acquired anti-HBs (from hepatitis B immune globulin or blood product administration) may be misinterpreted as active immunity 3
• Anti-HBs levels may decrease below detectable levels years after vaccination or natural infection, but immune memory may still provide protection 4, 5
• Different commercial assays may have varying sensitivities for detecting anti-HBs, potentially leading to different results in the same individual 4

Algorithm for Assessing HBV Immunity

1. Test for anti-HBs using a quantitative method

   • If ≥10 mIU/mL: Patient has protective immunity 1
   • If <10 mIU/mL: Proceed to step 2 1

2. Test for HBsAg and total anti-HBc to determine infection status

   • If HBsAg positive: Patient has active HBV infection (acute or chronic) 1
   • If HBsAg negative and anti-HBc positive: Patient likely had prior HBV infection with waning immunity 1
   • If HBsAg negative and anti-HBc negative: Patient is susceptible to HBV infection 1

3. For patients with anti-HBs <10 mIU/mL and negative HBsAg and anti-HBc:

   • Recommend vaccination or revaccination 1
   • Retest anti-HBs 1-2 months after completing vaccination series 1

4. For patients with isolated anti-HBc:

   • Consider testing for HBV DNA to rule out occult HBV infection 1
   • These patients are at higher risk for reactivation if exposed to immunosuppressants 1

By following this evidence-based approach, clinicians can accurately assess a patient's immunity to hepatitis B and take appropriate steps to ensure protection against HBV infection.