Synopsis
Interpret hepatitis B markers coherently, recognise acute and chronic infection, prevent onward and perinatal transmission, and start safe specialist-directed antiviral care when indicated.
- HBV spreads through infected blood and body fluids by perinatal, sexual, injecting, needlestick and inadequately sterilised equipment exposure.
- HBsAg indicates current infection; anti-HBc indicates natural exposure; anti-HBs alone usually indicates vaccine-derived immunity.
- IgM anti-HBc supports recent acute infection but may reappear during a severe chronic flare, so interpret the whole marker pattern and clinical timeline.
Key red flags
Confusion, drowsiness, asterixis, spontaneous bleeding, hypoglycaemia or rising INR requires emergency liver-failure management rather than routine outpatient referral.
Ascites, variceal bleeding, encephalopathy, jaundice or sarcopenia indicates advanced chronic liver disease requiring urgent specialist care.
Investigation priorities
Identify current hepatitis B infection in screening or diagnostic assessment.
Management branches
One or more hepatitis B markers are reported as reactive or equivocal.
- Confirm which markers were actually measured, the date of exposure or previous results, vaccination history, symptoms and immune-suppression status.
- Use HBsAg to identify current infection, anti-HBc for natural exposure and anti-HBs for immunity rather than interpreting any single result in isolation.
Key medicines
Tenofovir disoproxil fumarateGive 245 mg orally once daily for chronic HBV when selected by a specialist; duration is usually long term and stopping requires a defined virological and clinical plan.
EntecavirGive 0.5 mg orally once daily on an empty stomach in nucleoside-naive compensated disease; use the specialist 1 mg regimen for defined lamivudine resistance or decompensation.