What is being tested?
Hepatitis A antibody is produced in response to an infection with the hepatitis A virus. Hepatitis A is a highly contagious liver infection caused by the hepatitis A virus (HAV). It is one of several various causes of hepatitis, a condition characterised by inflammation and enlargement of the liver. Hepatitis A is one type of "hepatitis virus" identified so far; others including hepatitis B, C, D, and E are also known to cause hepatitis.
Hepatitis A is spread through food or water contaminated with the virus or by coming in contact with an infected person. While hepatitis A can cause a severe, acute disease, it does not cause a chronic infection as do some of the other hepatitis viruses. If you are exposed to hepatitis A, your immune system produces antibodies in response to the virus. This test detects hepatitis A antibodies in the blood.
While hepatitis has many different causes, the signs and the symptoms are broadly the same. In hepatitis, the liver is damaged and unable to function normally. It cannot process toxins or waste products such as bilirubin normally for removal from the body. During the course of the disease, bilirubin and liver enzyme levels in the blood can increase. While tests such as bilirubin or a liver function tests can tell your doctor that you have hepatitis, they will not tell s/he what is causing it. Antibody tests for hepatitis viruses may help determine the cause.
If you are exposed to hepatitis A, your body will first produce hepatitis A IgM antibodies. These antibodies typically develop 2 to 3 weeks after first being infected and persist for about 2 to 6 months. They are usually present 5-6 days prior to onset of symptoms. Hepatitis A IgG antibodies are produced within 1 to 2 weeks of the IgM antibodies and usually persist for life. Hepatitis A IgM antibodies develop early in the course of infection. The presence of hepatitis A IgM antibodies suggests acute hepatitis A but is only diagnostic if taken in the right clinical context. A positive hepatitis A IgM together with the presence of grossly abnormal liver function tests demonstrating hepatitis, the presence of symptoms such as nausea, fever, malaise, abdominal discomfort or a history of significant contact with a confirmed case is consistent with acute Hepatitis A. A positive Hepatitis A IgM is also seen in patients who have received the Hepatitis A vaccine in the days or weeks prior to testing and therefore the result should not be interpreted as evidence of acute disease. Testing for immunity to Hepatitis A can also be performed. Acute hepatitis is also caused by a number of other infectious and non-infectious agents and the choice of tests to use depends on the clinical scenario.
How is it used?
There are two versions of the test but both detect antibodies. Antibodies are produced by the body to protect itself from antigens (foreign proteins).
When is it requested?
Testing for the presence of IgM antibodies to hepatitis A is done if you have the symptoms or are likely to have been exposed to the virus. If you are being considered for the HAV vaccine, an antibody test may be requested before you are given the vaccine to see if you need it (if the antibodies are already present, the vaccine won’t help you). Once you have completed the two doses of the vaccine, the antibody test might be repeated to see if you have responded to the vaccine but this is usually not necessary.
What does the result mean?
About 30% of adults over age 40 have antibodies to HAV. If you have been given the vaccine, a positive result means you are immune to HAV and cannot be infected by it. See the table below for further interpretation of results.
|Total HAV antibody (IgM and IgG)
|Acute HAV infection or recent Hepatitis A vaccination
|No active infection, but previous HAV exposure; has developed immunity to HAV
|Has been exposed to HAV but does not rule out acute infection
|No current or previous HAV infection; no immunity to Hepatitis A; vaccine may be recommended if at risk
Is there anything else I should know?
It is presumed that one infection with hepatitis A produces lasting immunity against further infections with Hepatitis A.
The virus is found in faeces and contaminated water. You may have eaten raw fruit or vegetables handled by an infected person who did not wash their hands properly or you may have eaten raw or improperly cooked seafood that had fed in contaminated waters. Children are often infected by HAV and either do not become sick or have very mild symptoms such as fever and diarrhoea and are often thought to have ‘flu’.
You can spread the disease to others from the time you are first infected up until symptoms begin to appear which can be about 4 weeks. Generally adults are contagious for 2 weeks after contracting the disease. Children and people who are immunocompromised may be contagious for up to 6 months.
Yes. There is a vaccine available. It is recommended for people travelling to specific countries, and for those who have damage to their liver from some other cause.
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