Hepatitis A virus (HAV) is a small, 27 nm RNA virus. It is transmitted primarily by the fecal-oral route, either through person-to-person contact or ingestion of contaminated food or water. The incidence in the United States has dropped significantly since introduction of an effective vaccine. Occasional outbreaks of food borne hepatitis A still occur in the United States due to importation of contaminated food products. Blood-borne transmission is possible, but rare. Worldwide, more than 1 million acute infections occur per year. Travelers to areas of the world with high transmission rates of hepatitis A (e.g. Central and South America, Eastern Europe, and parts of Asia) should consider vaccination, if not previously immune.
Hepatitis A is generally a self-limited infection that does not have a chronic phase. Symptoms of hepatitis A infection include nausea, vomiting, abdominal pain, fever, jaundice, & pruritus. Hepatitis A infection is typically self-limited and does not lead to chronic liver disease or to a persistent carrier state. There is a 1% incidence of fulminant liver failure due to acute hepatitis A infection, predominantly in patients with underlying liver disease.
The incubation period is short, averaging 28 days and ranging from 15 to 45 days. The virus can be shed in feces for up to six months, and is transmissible for 2 weeks prior to the onset of symptoms.
Serum IgM antibody to the hepatitis A virus appears at about four weeks after initial infection and is usually detectable at the time of symptom onset. It remains detectable for 3 to 6 months following an acute infection. Occasionally HAV IgM antibodies persist for years. 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
False positive results occur more often in older females.
Hepatitis A IgG antibodies become detectable early in the convalescent phase of an acute infection or post-vaccination. Hepatitis A IgG antibody is detectable for decades following vaccine or infection, and a reactive result is indicative of protective immunity.
For diagnosis of acute hepatitis A infection, physicians should order both hepatitis A IgM and hepatitis A IgG antibodies. For confirmation of immunity, hepatitis A IgG antibody is the test of choice.
Results are reported as positive or negative. Reference value is negative.
Specimen requirement is one red top serum gel tube of blood