## Acute Hepatitis B Serology Pattern **Key Point:** The most common serological pattern in acute HBV infection is **HBsAg+, anti-HBc IgM+, anti-HBs−**. This triad defines the acute phase and is the diagnostic hallmark. ### Timeline of Marker Appearance 1. **HBsAg** — appears first (1–10 weeks after exposure); marks active infection 2. **Anti-HBc IgM** — appears shortly after HBsAg; indicates recent/acute infection (most specific for acute phase) 3. **Anti-HBc total** — persists for life after infection 4. **HBeAg** — appears early, indicates high infectivity 5. **Anti-HBs** — appears late during recovery; marks immunity ### Serological Patterns at a Glance | Phase | HBsAg | Anti-HBc IgM | Anti-HBc Total | Anti-HBs | Interpretation | |-------|-------|--------------|----------------|----------|----------------| | **Acute (early)** | + | + | + | − | Acute HBV (diagnostic window) | | **Acute (recovery)** | − | + | + | + | Resolving acute HBV | | **Chronic** | + | − | + | − | Chronic HBV carrier | | **Immune (vaccinated)** | − | − | − | + | Vaccination/resolved | | **Diagnostic window** | − | + | + | − | Recent infection, HBsAg cleared but anti-HBs not yet formed | **High-Yield:** Anti-HBc IgM is the **most specific marker for acute HBV infection** and is positive only in acute phase (typically 6 months). It is absent in chronic carriers and vaccinated individuals. **Clinical Pearl:** The "diagnostic window" occurs when HBsAg has cleared but anti-HBs has not yet appeared. During this brief period, **anti-HBc IgM is the only positive marker** and is critical for diagnosis. **Mnemonic: ACUTE HBV = HAM** - **H** — HBsAg (earliest marker) - **A** — Anti-HBc IgM (most specific for acute) - **M** — Markers appear in sequence [cite:Harrison 21e Ch 304]
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