Diagnosis
Identification
On the basis of clinical or epidemiologic features alone, hepatitis
A cannot be distinguished from other types of viral hepatitis.
Serologic testing is required to confirm diagnosis. Acute HAV
infection is confirmed by the presence of anti-HAV IgM antibody
to serum. IgM generally becomes detectable 5 to 10 days before
the onset of symptoms and can persist for up to 6 months.
Pre-vaccination serologic testing
HAV infection produces lifelong immunity to hepatitis A. A person
with serologic evidence of past HAV infection would derive no
benefit of vaccination.
Testing of children is not indicated because of their expected
low prevalence of infection. Testing may be considered for some
adults and older adolescents who have lived for an extensive
period of time in a geographic area that has a high endemic rate
of HAV infection or were born in these areas. These areas include
Central or South America, Africa, Asia and certain population
groups that include Native Americans, Alaskan Natives, and Hispanics.
Post-vaccination serologic testing
Testing of adults and children is not indicated because of the
high rate of vaccine response. Testing methods that are sufficiently
sensitive to detect low anti-HAV concentrations after vaccination
are not approved for routine diagnostic use in the United States.
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