hepatitis b in primary care: who to test, how to interpret, when to refer

Hepatitis B (HBV) is often asymptomatic until late disease. Primary care priorities are: (1) identify who needs testing, (2) use a minimum serology set to interpret status, (3) vaccinate susceptible people at risk, and (4) refer all HBsAg-positive people for specialist assessment and long-term monitoring.

• Born/raised in intermediate/high prevalence countries; people with household/sexual exposure risk.
• Current/past injecting drug use (including image/performance-enhancing drug injection).
• Men who have sex with men; sex work; multiple sexual partners; sexual assault.
• People in prison, homelessness, or where blood-borne virus prevalence is higher.
• Pregnancy (via antenatal screening, but GPs may encounter results).
• Before immunosuppression (biologics, chemotherapy) or if unexplained LFT abnormalities with risk factors.

Initial test set (minimum): HBsAg and anti-HBc (total/core antibody). Add anti-HBs for immune/vaccine status.

• HBsAg positive → current infection (acute or chronic). Refer for specialist work-up and monitoring.
• HBsAg negative + anti-HBc positive → previous exposure; add anti-HBs (immune) and consider reactivation risk if immunosuppressed.
• HBsAg negative + anti-HBc negative + anti-HBs positive → vaccinated immunity.
• All negative → susceptible; offer vaccination if at risk.

If HBsAg positive, specialist pathways typically request HBeAg/anti-HBe, HBV DNA, LFTs, FBC/platelets, clotting, and co-infection screen (HCV/HDV/HIV), plus liver imaging per guidance.

• Vaccination: offer to people at increased risk (use UKHSA Green Book schedules and local commissioning routes).
• Pregnancy: HBsAg-positive pregnant women require specialist assessment promptly to plan third-trimester antiviral treatment where indicated and neonatal prophylaxis.
• Urgent referral: suspected acute severe hepatitis, decompensated liver disease (ascites, encephalopathy, GI bleed), or jaundice with systemic illness.