A 22-year-old medical student develops malaise, nausea and dark urine two weeks after returning from a rural posting. Liver enzymes show ALT of 1200 U/L. Serology: anti-HAV IgM positive, anti-HAV IgG negative, HBsAg negative, anti-HCV negative. Which finding confirms that this is an acute hepatitis A infection?
- A ALT level above 1000 U/L
- B Presence of anti-HAV IgM in serum ✓
- C Absence of HBsAg
- D Dark urine with conjugated hyperbilirubinemia
Correct answer: B. Presence of anti-HAV IgM in serum
Explanation
Anti-HAV IgM appears at the onset of symptoms and persists for about 3 to 6 months, making it the standard marker of acute hepatitis B. Anti-HAV IgG indicates past infection or vaccination and confers lifelong immunity. High ALT occurs in all acute hepatitides and does not identify the agent. Hepatitis B never causes chronic carriage, so there is no carrier state to distinguish from.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
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Written and medically reviewed by the StethoPrep medical team.