What tests are recommended for diagnosing and managing hepatitis A and B?

Diagnostic Testing for Hepatitis A and B

For hepatitis B screening, test HBsAg, anti-HBs, and total anti-HBc; for hepatitis A, test IgG anti-HAV in patients under 50 years old. 1

Hepatitis B Testing Strategy

Initial Screening Panel

• HBsAg (Hepatitis B surface antigen): Detects active infection (acute or chronic) 1
• Anti-HBs (Antibody to HBsAg): Identifies immunity from vaccination or resolved infection 1
• Total anti-HBc (Antibody to core antigen): Distinguishes natural infection from vaccine-induced immunity 1

Interpretation of Initial Results

If HBsAg positive:

• Add IgM anti-HBc to distinguish acute from chronic infection 1
  • IgM anti-HBc positive = acute infection
  • IgM anti-HBc negative (only total anti-HBc positive) = chronic infection
• HBV DNA quantification to assess viral replication 1
• HBeAg and anti-HBe to determine disease phase 1
• ALT/AST levels to assess liver inflammation 1

If HBsAg persists beyond 6 months: Diagnosis of chronic hepatitis B is confirmed 1

If isolated anti-HBc positive (HBsAg negative, anti-HBs negative):

• Measure HBV DNA to rule out occult hepatitis B, especially in immunocompromised patients 1
• Repeat testing of HBsAg, anti-HBs, and anti-HBc in 3-6 months 1

Additional Testing for Chronic Hepatitis B Management

Once chronic infection is established, comprehensive evaluation includes:

• HBV DNA quantification using real-time PCR (sensitivity 10-10^8 IU/mL) 1

  • HBeAg-positive CHB: threshold ≥20,000 IU/mL indicates active replication 1
  • HBeAg-negative CHB: threshold ≥2,000 IU/mL indicates active disease 1

• Liver function tests: Complete blood count, ALT/AST, alkaline phosphatase, bilirubin, albumin, prothrombin time 1

• Coinfection screening for at-risk individuals 1:

  • Anti-HCV (hepatitis C)
  • Anti-HDV (hepatitis D, particularly in injection drug users)
  • Anti-HIV

• HCC surveillance in all HBsAg-positive persons ≥20 years old: baseline ultrasound and alpha-fetoprotein 1

• Fibrosis assessment: Transient elastography or liver biopsy in patients with elevated ALT 1

Hepatitis A Testing Strategy

Who to Test

• All chronic hepatitis B patients under 50 years old should be tested for IgG anti-HAV 1
• Patients with any chronic liver disease 2, 3

Rationale

Acute hepatitis A superinfection in patients with chronic hepatitis B causes more severe disease, acute hepatic failure, and higher fatality rates 2, 3. The anti-HAV seroprevalence in younger populations has declined significantly, making screening cost-effective 1.

Testing Approach

• IgG anti-HAV or total anti-HAV antibodies: Identifies immunity from prior infection 1, 2
• If negative, administer 2 doses of hepatitis A vaccine at 0 and 6-12 months 1

Acute Hepatitis A Diagnosis

• IgM anti-HAV: Diagnostic marker for acute infection 4, 5
• Should be accompanied by elevated serum transaminases (97% sensitivity) 5

Critical Pitfalls to Avoid

Window period confusion: Isolated IgM anti-HBc may be the only marker during the window period between HBsAg disappearance and anti-HBs development, particularly in severe or fulminant hepatitis B 1. Follow with repeat testing in 3-6 months.

Occult hepatitis B: Isolated total anti-HBc (without HBsAg or anti-HBs) may represent occult infection, especially in immunocompromised patients—always measure HBV DNA in this scenario 1.

Transient HBsAg positivity: Can occur up to 18 days post-vaccination and is clinically insignificant 1.

Postvaccination testing: Not routinely needed for healthy adults, but mandatory for patients with chronic liver disease due to lower seroconversion rates 2, 3. Test anti-HBs 1-2 months after completing the vaccine series 1.

Serial monitoring: Use the same HBV DNA assay consistently for a given patient to ensure accurate comparison over time 1.