serology

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There is a rise in serum transaminases 22-40 days after exposure.

Serum antibody to HAV appears as the stool becomes negative for virus:

  • serum IgM anti-HAV
    • implies recent infection
    • detectable about 3 weeks after exposure and increases in titre over 4–6 weeks, it persists for 2-6 months (rarely for up to one year) in low titre then declines to non-detectable levels (2)
    • negative tests should be repeated if taken <5 days after the onset of symptoms to exclude a false-negative result (3)
    • when the test result is reactive but probable non-specific IgM reactivity, repeat the test (3)
    • false positive IgM are more common in the elderly and should be interpreted with caution (since they are likely to have had hepatitis A in childhood) (4)
  • serum IgG anti-HAV
    • persists for many years (usually lifelong)
    • probably conveys immunity to further infection with HAV (1)

Other investigations include:

  • serum/plasma alanine aminotransferase (ALT) and aspartate aminotransferase (AST) levels – 500-10,000 i.u./l
  • billirubin – upto 500 micromoles/litre
  • alkaline phosphatase levels
  • prothrombin time – if prolonged for more than 5 seconds suggests developing hepatic decompensation (5)

Reference:

Last reviewed 01/2018