Serology

HBsAg (surface antigen)

• this is the earliest indicator of HBV appearing 27-41 days after infection
• may occur before icterus is clinically evident
• persistence beyond 6 months defines a chronic infection
  • up to 50% of people with extended chronic infection will eventually clear HBsAg.
  • those with resolving acute HBV will clear HBsAg several months after initial infection.

anti-HBsAg (surface antibody)

• rises once the acute disease is over and convalescence has started
• levels are rarely high and are undetectable in 10-15% of patients with acute HBV
• there is a gap of several weeks to months between the disappearance of HBsAg and the appearance of anti-HBs
  • during this period, anti-HBc total is detectable as a marker of HBV infection.

HBeAg

• indicates acute HBV infection
• normally present for a shorter time than HBsAg
• seen soon after transaminase levels peak (i.e. after HBsAg)
• persistence indicates continued active viral replication and continued infectivity.

anti-HBe

• indicates relatively low infectivity
• suggests recovery from acute infection
  • but may occur in carriers and is generally a marker of reduced viral replication, indicating a less infectious state (1)

HBcAg - not detectable in the blood.

anti-HBc

• IgM anti-HBc:
  • high titres indicate acute infection
  • low titres indicate ongoing disease, usually chronic active hepatitis
• IgG anti-HBc:
  • with +ve HBsAg indicates chronic HBV hepatitis
  • with -ve HBsAg indicates infection in the remote past HBV DNA - indicates a continued infectious state. PCR provides a highly sensitive and rapid method for it's detection.

The presence of concomitant infection with hepatitis D should be excluded in all patients with HBV infection.

Reference:

• (1) Public Health Agency of Canada. Primary care management of hepatitis B – Quick reference 2013