What does a positive Hepatitis B (HBV) core antibody test indicate?

Why Hepatitis B Core Antibody is Positive

A positive hepatitis B core antibody (anti-HBc) indicates that you have been infected with hepatitis B virus (HBV) at some point in your life—either currently or in the past—but this test alone cannot distinguish between acute, chronic, or resolved infection. 1, 2

What Anti-HBc Actually Means

• Anti-HBc appears during acute HBV infection and typically persists for life, regardless of whether the infection resolves or becomes chronic 2
• This antibody is the most sensitive indicator of HBV infection because the core antigen is highly immunogenic and virtually always induces antibodies in immunocompetent infected persons 3, 4
• The total anti-HBc test includes both IgM and IgG antibodies to the hepatitis B core antigen, which is why it remains positive long-term 2

Required Additional Testing to Determine Your Status

You cannot interpret anti-HBc in isolation. The following tests are essential to determine what a positive anti-HBc means for you: 1, 2

• HBsAg (hepatitis B surface antigen) - indicates active infection
• Anti-HBs (hepatitis B surface antibody) - indicates immunity
• IgM anti-HBc - distinguishes acute from chronic/past infection
• HBV DNA - if HBsAg is positive or if immunosuppression is planned

Four Main Interpretations Based on Complete Testing

Pattern 1: Acute HBV Infection

• HBsAg positive + Total anti-HBc positive + IgM anti-HBc positive 1, 2
• This means you have a new, active infection that your body is currently fighting

Pattern 2: Chronic HBV Infection

• HBsAg positive + Total anti-HBc positive + IgM anti-HBc negative (or low-level) 1, 2
• This means you have ongoing infection that has persisted beyond 6 months
• Requires referral to a hepatology specialist for management decisions 2

Pattern 3: Resolved Infection with Immunity (Most Common)

• HBsAg negative + Total anti-HBc positive + Anti-HBs positive 1, 2, 5
• This is the most likely scenario—you had HBV in the past, cleared it, and now have natural immunity 5
• You are not currently infectious and generally not at risk for chronic infection 5

Pattern 4: Isolated Anti-HBc (Requires Careful Evaluation)

• HBsAg negative + Total anti-HBc positive + Anti-HBs negative 1, 5
• This pattern may represent:
  • Resolved infection with waning anti-HBs antibodies over time 1
  • False-positive anti-HBc test 6
  • Window period of acute infection (rare) 1, 6
  • Occult HBV infection with very low viral levels 1

Critical Warning: Reactivation Risk with Immunosuppression

Even if you have resolved HBV infection (HBsAg negative, anti-HBc positive), you remain at risk for viral reactivation if you become immunosuppressed. 7, 5

• The virus persists as cccDNA in hepatocytes even after apparent clearance, which can reactivate when immunity is suppressed 7
• Reactivation risk ranges from 3-45% depending on the immunosuppressive regimen 1, 5
• Highest risk occurs with:
  • Anti-CD20/CD52 monoclonal antibodies (rituximab) 1, 5
  • High-dose corticosteroids 1, 5
  • Hematopoietic stem cell transplant 1
• Reactivation can occur up to 6-12 months after stopping immunosuppression, particularly with rituximab 7

Before Starting Immunosuppressive Therapy:

• Measure HBV DNA level to define reactivation risk 5
• Consider antiviral prophylaxis if HBV DNA is detectable 1, 5
• Monitor liver function tests during and after therapy 5

Essential Next Steps

• Screen and vaccinate all household and sexual contacts for HBsAg and anti-HBs; vaccinate seronegative contacts immediately 1
• Test for coinfections: HAV serology, HCV, and HIV in at-risk individuals 1
• If HBsAg positive, measure HBV DNA level, ALT/AST, and HBeAg/anti-HBe to assess disease activity 1
• Counsel on transmission prevention: avoid heavy alcohol use (accelerates progression to cirrhosis), cover open wounds, clean blood spills with bleach 1

Common Pitfalls to Avoid

• Never assume anti-HBs provides complete protection against reactivation—even patients with anti-HBs positive can reactivate under potent immunosuppression, though risk is lower with titers >100 IU/mL 7
• Passively acquired anti-HBs from blood products can give false reassurance—this does not indicate true immunity 8
• Some chronically infected patients may have undetectable anti-HBc with standard assays, though this is rare 3
• Anti-HBc can persist for life but may wane over decades, leading to isolated anti-HBc patterns that require careful interpretation 6, 4