Paper I
2023 July (Supplementary) (2019 Scheme) · 100 marks · 180 min

Question

Write the serological markers of Hepatitis B virus infection and their significance.

Q84 marksShort Answers

Answer

Serological markers of Hepatitis B virus infection and their significance:

  • HBsAg — first marker to appear; indicates current infection (acute or chronic if >6 months); basis of the vaccine.
  • Anti-HBs — indicates recovery with immunity, or successful vaccination.
  • IgM anti-HBc — indicates recent/acute infection; the only detectable marker during the “window period” (when HBsAg has cleared but anti-HBs has not yet risen).
  • IgG anti-HBc — persists long-term, indicating past or current infection (absent after vaccination, distinguishing natural infection from vaccine-induced immunity).
  • HBeAg — marker of active viral replication and high infectivity.
  • Anti-HBe — appearance generally indicates reduced replication/infectivity (precore mutants an exception).
  • HBV DNA (quantitative PCR) — the most direct marker of active viral replication, used for monitoring disease activity and treatment response.

Typical patterns: acute infection — HBsAg+, IgM anti-HBc+; window period — only IgM anti-HBc+; chronic infection — HBsAg+ (>6 months), IgG anti-HBc+; resolved infection — anti-HBs+, IgG anti-HBc+; vaccinated — anti-HBs+ only, anti-HBc negative.

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