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If Hepatitis A Antibody Total is elevated, reflexes to Hepatitis A Antibody IgM.
Hepatitis A virus (HAV) is endemic throughout the world, however, occurring most commonly in areas of poor hygiene and low socioeconomic conditions. The virus is transmitted primarily by the fecal-oral route, and it is spread by close person-to-person contact and by food- and water-borne epidemics. Viral spread by parenteral routes (e.g., exposure to blood) is possible but rare, because infected individuals are viremic for a short period of time (usually <3 weeks). There is little or no evidence of transplacental transmission from mother to fetus or transmission to newborn during delivery.
Limitations • The results determined by different assays from different manufacturers can vary due to differences in assay specificities and cannot be used interchangeably. • Assay performance characteristics have not been evaluated for immunocompromised, immunosuppressed, infants, children or adolescent patients. • A reactive or positive result does not exclude co-infection by another hepatitis virus.
Antibodies to HAV (anti-HAV) are detectable by the time symptoms occur, usually 15 to 45 days after exposure. The early antibody response is largely comprised of the IgM antibody subclass. Anti-HAV IgM is detectable for 3 to 6 months after the onset of illness, whereas anti-HAV IgG can persist indefinitely. The specific determination of anti-HAV IgM is the most useful serological marker for diagnosing acute HAV infection. Total anti-HAV is used primarily for determination of previous exposure to Hepatitis A virus. The measurement of anti-HAV total activity is also used to identify HAV susceptible individuals for vaccination. Positive results should be correlated with the patient’s clinical history.
A positive anti-HAV total result with a negative anti-HAV IgM result indicates immunity to hepatitis A from either past/resolved hepatitis A or vaccination against hepatitis A. Hepatitis A is a reportable disease in Wisconsin and other states.