Which feature best distinguishes acute hepatitis B from acute hepatitis A in an Indian patient presenting with jaundice and elevated transaminases?

Question

Accepted Answer

B. Presence of anti-HBc IgM antibodies. ## Distinguishing Acute Hepatitis B from Acute Hepatitis A

### Key Serological Markers

**Key Point:** Anti-HBc IgM is the most reliable early marker of acute hepatitis B infection and appears during the window period when HBsAg is positive but anti-HBs has not yet developed.

### Comparative Table: Hepatitis A vs Hepatitis B

| Feature | Hepatitis A | Hepatitis B |
| --- | --- | --- |
| **Transmission** | Fecal-oral (contaminated water/food) | Parenteral, sexual, vertical |
| **Acute fulminance** | <1% (except in elderly/cirrhotic) | 0.1–0.5% in immunocompetent |
| **Chronicity** | Never (100% resolution) | 5–10% in adults, 90% in neonates |
| **Early marker (acute phase)** | Anti-HAV IgM | Anti-HBc IgM |
| **Window period marker** | None (anti-HAV IgM bridges to anti-HAV IgG) | Anti-HBc IgM (HBsAg negative, anti-HBs negative) |
| **Histology** | Acute inflammation, no bridging necrosis | Acute inflammation, may have bridging necrosis |

### Clinical Pearl

**High-Yield:** Anti-HBc IgM is the **gold standard** for diagnosing acute HBV infection, especially in the window period (first 4–6 weeks) when HBsAg may be transiently negative but the patient is still infectious. This is the single best discriminator between acute HAV and acute HBV.

### Why Other Features Do Not Distinguish

- **Fulminant failure:** Rare in both; HAV can cause fulminance in elderly/cirrhotic patients, HBV rarely in immunocompetent adults. Not a reliable discriminator.
- **Fecal-oral transmission:** This is HAV's hallmark, but the question asks what **distinguishes** acute HBV from HAV — this feature is present in HAV, not HBV, so it does not help identify which virus is causing the acute illness in a given patient.
- **Complete resolution:** Both HAV and acute HBV resolve completely in the acute phase in immunocompetent hosts; chronicity develops later in HBV. Not a feature of acute illness.

Answer

A. Fecal-oral route of transmission

Answer

C. Complete resolution without chronic sequelae

Answer

D. Fulminant hepatic failure in >50% of cases

Which feature best distinguishes acute hepatitis B from acute hepatitis A in an Indian patient presenting with jaundice and elevated transaminases?

Explanation

Distinguishing Acute Hepatitis B from Acute Hepatitis A

Key Serological Markers

Comparative Table: Hepatitis A vs Hepatitis B

Clinical Pearl

Why Other Features Do Not Distinguish

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Feature	Hepatitis A	Hepatitis B
Transmission	Fecal-oral (contaminated water/food)	Parenteral, sexual, vertical
Acute fulminance	<1% (except in elderly/cirrhotic)	0.1–0.5% in immunocompetent
Chronicity	Never (100% resolution)	5–10% in adults, 90% in neonates
Early marker (acute phase)	Anti-HAV IgM	Anti-HBc IgM
Window period marker	None (anti-HAV IgM bridges to anti-HAV IgG)	Anti-HBc IgM (HBsAg negative, anti-HBs negative)
Histology	Acute inflammation, no bridging necrosis	Acute inflammation, may have bridging necrosis