What tests are used to diagnose hepatitis B (HB)?

Testing for Hepatitis B

The primary test for diagnosing hepatitis B is hepatitis B surface antigen (HBsAg), which should be performed using an FDA-licensed serologic assay, with initially reactive specimens confirmed by a neutralizing confirmatory test. 1

Core Serologic Tests for Initial Diagnosis

The essential serologic markers to differentiate among acute, chronic, and resolved hepatitis B infection are: 1

• HBsAg (Hepatitis B Surface Antigen): The hallmark marker of active HBV infection 2

  • Detectable 30 days after exposure (range: 6-60 days) 1
  • Persistence for >6 months defines chronic infection 1, 2
  • First serologic marker to appear in acute infection 3

• Anti-HBc (Antibody to Hepatitis B Core Antigen): Indicates current or previous infection 2

  • IgM anti-HBc: Indicates acute or recent infection when positive 1, 2
    • Appears at symptom onset and persists up to 6 months in acute infection 1
    • Should only be tested in persons with clinical evidence of acute hepatitis or epidemiologic link to HBV, as positive predictive value is low in asymptomatic persons 1
  • Total anti-HBc: Persists for life after infection 1, 2

• Anti-HBs (Antibody to Hepatitis B Surface Antigen): Indicates recovery from infection or successful vaccination 2

  • Appears after HBsAg clearance in recovered patients 1

Additional Markers for Disease Assessment

Once chronic infection is confirmed, these tests assess viral replication and disease activity: 1

• HBeAg (Hepatitis B e Antigen): Marker of high viral replication 1, 2

  • Typically indicates HBV DNA levels of 10⁶-10¹⁰ IU/mL 1

• Anti-HBe (Antibody to HBeAg): Usually indicates lower viral replication 1, 2

  • Generally associated with HBV DNA levels of 0-10⁵ IU/mL 1

• HBV DNA Quantification: Essential for assessing viral replication, disease activity, and treatment decisions 1, 2

  • HBeAg-positive chronic hepatitis B: typically ≥20,000 IU/mL 1, 2
  • HBeAg-negative chronic hepatitis B: typically ≥2,000 IU/mL 1, 2
  • Inactive carrier state: <2,000 IU/mL 1, 2
  • More sensitive than HBsAg, detectable 10-20 days before HBsAg appears 1

Liver Function and Additional Tests

Complete initial evaluation requires: 1, 2

• Liver enzymes: ALT/AST to assess hepatic inflammation 2
• Liver function tests: Bilirubin, albumin, prothrombin time/INR 2
• Complete blood count 1
• Alkaline phosphatase and gamma-glutamyl transpeptidase 2

Coinfection Screening

Test for other hepatotropic viruses and relevant coinfections: 2

• Anti-HCV: Rule out hepatitis C coinfection 2
• Anti-HDV: In patients with injection drug use history or from endemic areas 2
• Anti-HIV: In high-risk groups 2
• Anti-HAV IgG: Determine immunity status; vaccinate if negative 2

Interpretation of Common Serologic Patterns

• Acute HBV infection: HBsAg positive, IgM anti-HBc positive 1, 2
• Chronic HBV infection: HBsAg positive for >6 months, total anti-HBc positive, IgM anti-HBc negative 2
• Past infection with immunity: HBsAg negative, anti-HBs positive, total anti-HBc positive 2
• Vaccine-induced immunity: HBsAg negative, anti-HBs positive, total anti-HBc negative 2
• Window period: Both HBsAg and anti-HBs negative, but IgM anti-HBc positive 2

Special Testing Scenarios

Isolated anti-HBc positivity (only anti-HBc detectable) can represent: 1

• Resolved infection with waned anti-HBs levels (most common in high-prevalence populations) 1
• Chronic infection with undetectable HBsAg (occult hepatitis B) 1
• False-positive reaction 1
• Requires repeat testing of HBsAg, anti-HBs, and anti-HBc in 3-6 months 1
• Consider HBV DNA testing to clarify 1

Occult HBV infection: Detectable HBV DNA with negative HBsAg 1, 3

• Test in cryptogenic liver disease with anti-HBc positivity 1
• Test prior to immunosuppression 1
• Test in solid organ transplant donors with isolated anti-HBc 1

Critical Pitfalls to Avoid

• Do not miss the window period: When both HBsAg and anti-HBs are negative, IgM anti-HBc is the only marker present 2
• Do not misinterpret isolated anti-HBc: Requires follow-up testing and possibly HBV DNA measurement 2
• Do not underestimate HBeAg-negative chronic hepatitis B: Can have lower HBV DNA levels (≥2,000 IU/mL) but still cause progressive liver disease 1, 2
• Do not test IgM anti-HBc in asymptomatic persons: Low positive predictive value; reserve for those with clinical acute hepatitis or epidemiologic link 1
• Transient HBsAg positivity: Can occur up to 18 days after hepatitis B vaccination and is clinically insignificant 1

Monitoring Recommendations

For untreated chronic HBV patients: 2

• ALT every 3-6 months 2
• HBV DNA every 6-12 months 2
• HBeAg/anti-HBe status annually 2

For cirrhotic patients: 2

• More frequent monitoring required 2
• HCC surveillance with ultrasound every 6 months 2
• Alpha-fetoprotein for baseline HCC screening 2