In the serological diagnosis of hepatitis A, which marker is FIRST to appear and best indicates acute HAV infection?
- A Anti-HAV IgG
- B Anti-HAV IgM, detectable from the onset of symptoms ✓
- C HAV RNA by PCR (rises during incubation before symptoms)
- D HAV p27 antigen by ELISA
Correct answer: B. Anti-HAV IgM, detectable from the onset of symptoms
Explanation
Anti-HAV IgM is the serological marker of choice for diagnosing acute hepatitis A; it appears at the onset of symptoms (about 4 weeks after exposure), peaks early and then declines over 3–6 months. Anti-HAV IgG appears later, persists lifelong and indicates past infection or immunity. HAV RNA by PCR rises even earlier during the incubation period but requires molecular laboratory infrastructure and is not routinely done. HAV antigen assays are not used clinically. A positive anti-HAV IgM in a symptomatic patient confirms acute HAV.
Reference: Ananthanarayan & Paniker's Textbook of Microbiology, 11th ed.
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