What tests to run when Hepatitis B surface antigen (HBsAg) is positive?

Testing Protocol for Positive HBsAg Result

When a patient tests positive for Hepatitis B surface antigen (HBsAg), a comprehensive panel of additional tests should be ordered to determine the status of infection, assess liver damage, and guide appropriate management. 1

Essential Follow-up Tests

• Complete HBV serologic profile including:

  • Anti-HBc (total and IgM) - to distinguish between acute and chronic infection 1, 2
  • HBeAg and anti-HBe - to assess viral replication status and infectivity 1, 3
  • Anti-HBs - to evaluate immune status 1, 4
  • Quantitative HBV DNA - to determine viral load and monitor treatment response 1

• Liver function tests to assess liver damage:

  • ALT/AST, alkaline phosphatase, GGT, bilirubin, albumin, and prothrombin time 2, 3
  • Complete blood count and platelet count (low platelets may indicate advanced fibrosis) 2, 5

Interpretation of Results

• Acute HBV infection: Positive HBsAg and positive IgM anti-HBc 4, 6, 7
• Chronic HBV infection: Positive HBsAg for more than 6 months, positive total anti-HBc, negative anti-HBs 4, 2
• Resolved infection with immunity: Negative HBsAg, positive anti-HBs, positive anti-HBc 4
• Vaccine-induced immunity: Negative HBsAg, positive anti-HBs, negative anti-HBc 4

Additional Important Tests

• Screening for coinfections:

  • HIV testing - HBV/HIV coinfection requires specific management approaches 1, 5
  • Hepatitis C virus (HCV) antibody - to rule out HBV/HCV coinfection 1
  • Hepatitis D virus (HDV) antibody - particularly in high-risk populations 1

• Hepatitis A immunity status (anti-HAV total) - to determine need for HAV vaccination 4, 2

• Assessment of liver disease severity:

  • Ultrasound of the liver - to assess for cirrhosis and exclude focal lesions 3
  • Non-invasive fibrosis assessment (e.g., transient elastography) if available 1
  • Liver biopsy may be considered in selected cases but is not routinely required 1, 3

Clinical Considerations

• Confirmation of chronicity requires HBsAg positivity for at least 6 months - repeat testing is recommended 1, 2

• Patients with discrepant HBsAg results (e.g., positive quantitative but negative qualitative) should have repeat testing in 3-6 months 2

• The "window period" during acute HBV infection may show negative HBsAg but positive IgM anti-HBc 4, 6

• Isolated anti-HBc (negative HBsAg, negative anti-HBs, positive anti-HBc) requires careful interpretation and may necessitate HBV DNA testing 4, 2

• All HBsAg-positive patients should be educated about preventing transmission to others 1

• Contact tracing and vaccination of susceptible household members and sexual partners is recommended 1