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.
- Persistence of HBsAg for at least six months defines chronic infection; HBV DNA quantifies replication and informs infectivity and treatment.
- First assess INR, glucose, cognition and renal function in acute jaundice, then arrange urgent liver-centre care for failure features.
- Chronic treatment is specialist selected from HBV DNA, ALT, fibrosis, cirrhosis, pregnancy, renal or bone health, coinfection and future immunosuppression.
- Tenofovir disoproxil 245 mg orally once daily or entecavir 0.5 mg orally once daily are established high-barrier options in suitable adults.
- Vaccinate susceptible contacts, apply current UKHSA post-exposure criteria and ensure exposed infants receive the complete national perinatal schedule and follow-up testing.
Key red flags
Confusion, drowsiness, asterixis, spontaneous bleeding, hypoglycaemia or rising INR requires emergency liver-failure management rather than routine outpatient referral.
A pregnant person who is HBsAg positive needs prompt specialist viral-load assessment and a documented maternal and neonatal prevention plan before delivery.
A baby born to an HBsAg-positive mother requires hepatitis B vaccine within 24 hours and HBIG when current national criteria are met.
Immunosuppression, chemotherapy or B-cell-depleting therapy can reactivate resolved or chronic HBV and should never begin without HBV marker review and a prevention plan.
New jaundice or ALT flare in chronic HBV may represent immune-active disease, resistance, non-adherence, drug injury or hepatitis D superinfection.
Occupational, sexual or household blood exposure requires same-day risk assessment because vaccine and HBIG effectiveness is time dependent.
Ascites, variceal bleeding, encephalopathy, jaundice or sarcopenia indicates advanced chronic liver disease requiring urgent specialist care.
A sudden HBV DNA rise and ALT flare during or after immune suppression can progress to jaundice and liver failure.
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.
- Add IgM anti-HBc when acute disease is possible and quantitative HBV DNA when infection, reactivation, pregnancy or treatment assessment requires replication data.
- Discuss discordant or isolated anti-HBc patterns with virology because resolved infection, occult infection, window-period disease and false reactivity require different action.