There is a rise in serum transaminases 22-40 days after exposure. (1)
Serum antibody to HAV appears as the stool becomes negative for virus:
- serum IgM anti-HAV (2)
- 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
- negative tests should be repeated if taken <5 days after the onset of symptoms to exclude a false-negative result
- when the test result is reactive but probable non-specific IgM reactivity, repeat the test
- 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)
- serum IgG anti-HAV
- persists for many years (usually lifelong)
- probably conveys immunity to further infection with HAV (1)
Other investigations include: (3)
- serum/plasma alanine aminotransferase (ALT) and aspartate aminotransferase (AST) levels – 500-10,000 i.u./l
- bilirubin – up to 500 micromoles/litre
- alkaline phosphatase levels
- prothrombin time – if prolonged for more than 5 seconds suggests developing hepatic decompensation and severe infection.
Reference:
- Castaneda D, Gonzalez AJ, Alomari M, et al; From hepatitis A to E: A critical review of viral hepatitis. World J Gastroenterol. 2021 Apr 28;27(16):1691-1715.
- Nelson NP, Weng MK, Hofmeister MG, et al. Prevention of hepatitis A virus infection in the United States: recommendations of the Advisory Committee on Immunization Practices, 2020. MMWR Recomm Rep. 2020 Jul 3;69(5):1-38.
- United Kingdom National Guideline on the Management of the viral hepatitides A, B and C; British Association for Sexual Health and HIV (2015)