Hepatitis A Virus Antibody IgM
The hepatitis A virus (HAV) is a small, 27 nm RNA virus. It is transmitted primarily by the fecal-oral route, and is found more commonly in situations where unsanitary conditions and/or close contact among individuals exist. Contaminated food and water are frequent means of transmission. Although ~70% of children aged <6 years with HAV infection are asymptomatic, older children and adults usually have symptoms and 70% are jaundiced.
The incubation period is short, averaging 25 days and ranging from 15-45 days. Serum IgM antibody to the hepatitis A virus (anti-HAV) appears at about four weeks after initial infection and usually persists for 2-6 months as the initial phase of the immune response. Subsequently, only IgG antibodies are detected. Serum IgG antibody to HAV generally persists for lifetime, conferring immunity to further type A infection. HAV is typically self-limited and does not lead to chronic liver disease or to a persistent carrier state.
Measurement of the HAV IgM antibody is the preferred diagnostic test for acute infection. A positive IgM anti-HAV test result in a person without symptoms of hepatitis A might indicate:
- Asymptomatic acute HAV infection
- Previous hepatitis A infection with prolonged presence of IgM anti-HAV
- False positive test result
Results are reported as positive or negative. Reference value is negative.
Specimen requirement is one SST tube of blood.
