Overview
This lecture explains how to interpret hepatitis B serology results, focusing on understanding key antigens, antibodies, and their relevance in diagnosis and vaccination.
Antigens in Hepatitis B
- Hepatitis B surface antigen (HBsAg) is found on the virus surface; its presence in blood means active infection.
- The hepatitis B vaccine contains HBsAg to stimulate immunity.
- Hepatitis B e antigen (HBeAg) is present during active viral replication and indicates high infectivity.
- Hepatitis B core antigen (HBcAg) is located inside the virus and does not circulate in the blood; not detected on blood tests.
Antibodies in Hepatitis B
- Hepatitis B surface antibody (anti-HBs) appears after vaccination or infection and indicates immunity.
- Hepatitis B e antibody (anti-HBe) forms after the active replication phase, indicating reduced infectivity.
- Hepatitis B core antibody (anti-HBc) shows exposure to the virus; two types:
- IgM anti-HBc: indicates acute infection.
- IgG anti-HBc: indicates past or chronic infection.
Interpretation and Testing Strategy
- Test HBsAg for active infection.
- Test anti-HBc for previous or current infection.
- Test HBeAg to assess viral replication and infectivity.
- Test hepatitis B DNA to measure viral load directly.
Key Terms & Definitions
- Antibody — a protein made by B-cells that targets a specific antigen.
- Antigen — a substance (often a protein) that triggers an immune response.
- HBsAg (Hepatitis B surface antigen) — marker for current infection; used in vaccines.
- HBeAg (Hepatitis B e antigen) — marker for active replication and high infectivity.
- HBcAg (Hepatitis B core antigen) — internal protein; not measured in blood.
- Anti-HBs — antibody to surface antigen; indicates immunity.
- Anti-HBe — antibody to e antigen; signals reduced infectivity.
- Anti-HBc — antibody to core antigen; IgM signals acute, IgG signals past/chronic infection.
- Viral load (Hepatitis B DNA) — the amount of virus in the blood.
Action Items / Next Steps
- Review serology tables for hepatitis B interpretation.
- Practice interpreting sample hepatitis B serology results.
- Visit the recommended website for detailed resources on hepatitis and test your knowledge.