The serology, decoded
Three markers answer most questions:
- HBsAg (surface antigen) — current infection (acute or chronic)
- Anti-HBc (core antibody) — exposure to the virus (IgM = recent/acute; IgG = past or chronic). The vaccine does not produce anti-HBc
- Anti-HBs (surface antibody) — immunity (from vaccination or resolved infection)
Two more refine it:
- HBeAg — active replication, high infectivity
- HBV DNA — viral load, guides treatment
Pattern table
| HBsAg | Anti-HBc | Anti-HBs | Interpretation |
|---|---|---|---|
| + | IgM + | – | Acute hepatitis B |
| + | IgG + | – | Chronic hepatitis B |
| – | + (IgG) | + | Resolved past infection (immune) |
| – | – | + | Vaccinated (immune) |
| – | + | – | Past exposure / occult infection (or window period) |
Management of chronic HBV
- Nucleos(t)ide analogues: tenofovir or entecavir — high potency, high resistance barrier, first-line
- Pegylated interferon-alfa in selected patients (finite course; poorly tolerated)
- Treatment decisions use HBV DNA, ALT and fibrosis stage
- Hepatocellular carcinoma surveillance for all (6-monthly ultrasound ± AFP)
- Screen and vaccinate household/sexual contacts; test for hepatitis D and HIV co-infection
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