Hepatitis A Virus Antibodies
Hepatitis A virus (HAV) is a small, 27 nm RNA virus that is the most common cause of hepatitis worldwide. It is primarily transmitted fecal-orally after close contact with an infected. Outbreaks of hepatitis A virus infections used to occur every 10 to 15 years and primarily involved asymptomatic children. The widespread adoption of universal childhood vaccination has dramatically decreased these outbreaks (https://www.cdc.gov/mmwr/preview/mmwrhtml/rr5507a1.htm). Rates of HAV infection declined by approximately 95% between the years of 1996 and 2011.
During 2016–2018, CDC received approximately 15,000 reports of HAV infections from U.S. states and territories. The vast majority of these reports were related to multiple outbreaks of infections among persons reporting drug use, homelessness and men who have sex with men (MSM). A small number of cases have been caused by consumption of imported HAV-contaminated food. Historically, genotype IA has been the most common genotype circulating in North and South America. HAV genotype IB has been predominant in the most recent outbreaks. Increasing numbers of genotype IIIA were also seen, which used to be rare in the United States.
HAV 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.
HAV IgG antibodies become detectable early in the convalescent phase of an acute infection or post-vaccination. HAV IgG is detectable for decades following vaccine or infection, and a reactive result is indicative of protective immunity.
For diagnosis of acute HAV infection, physicians should order both hepatitis A IgM and hepatitis A IgG antibodies. For confirmation of immunity, HAV 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.
