Hepatitis B

Step 1: HBsAg (Surface Antigen)

Is there a current infection?

• YES → You currently have a Hepatitis B infection

• ⁠NO → Move to Step 2 to check for any past infection

Step 2: Anti-HBc (Core Antibody)

Have you ever been infected?

• YES → You’ve had a Hepatitis B infection at some point (past or current)

• NO → Move to Step 3 to see if you’re protected through vaccination

Step 3: Anti-HBs (Surface Antibody)

Do you have immunity?

• YES → You’re immune (either from vaccination or past infection).

• NO → You’re not protected - you’re susceptible and need vaccination.

Serology Interpretation

• Susceptible:

  • All serology negative

• Previous Infection:

  • HBsAg: negative

  • HBcAb+/HBsAb+: positive

• Previous Vaccination:

  • HBsAg and HBcAb: negative

  • HBsAb+: positive

• Acute Infection:

  • HBsAg+: positive

  • HBcAb+: IgM high titre

  • HBsAb: negative

• Chronic Infection:

  • HBsAg+: positive

  • HBcAb+: IgG low titre

  • HBsAb: negative

• Note: If only anti-HBc is positive with negative HBsAg and HBsAb, consider previous resolved infection, occult HBV infection, or false positivity (requires HBV DNA testing)

Non-Responder

• No current chronic Hep B infection

• History of age-appropriate Hep B vaccinations

• HBsAb <10 mIU/mL

• Management:

  • Booster (4th dose) → Test 4–5 weeks later

  • If still negative, give another 2 doses (1 month apart) and retest at 4 weeks post final dose (3 extra doses total)

  • Persistent non-responders require HBIG within 72 hrs for exposure

Testing for Hepatitis B

• Serological Testing:

  • Determines acute/chronic infection, resolved infection, vaccination immunity, or susceptibility

• Isolated Anti-HBc Positive:

  • Causes:

    • Previous infection (low-level anti-HBs undetectable)

    • Occult HBV infection (HBV DNA positive, HBsAg negative)

    • False-positive result

    • Resolving acute infection

• Who to Test:

  • Pregnant women (routine antenatal screening for HBsAg)

  • Household/sexual contacts of infected individuals

  • People at risk (e.g., migrants from intermediate/high-prevalence countries)

  • All patients with elevated liver enzymes without clear explanation

  • Co-infection screening (Hep B, Hep C, Hep D, and HIV is recommended)

• Follow-Up and Notification:

  • Acute Hepatitis B must be notified to public health authorities

  • Chronic Hepatitis B notification varies by jurisdiction