Hepatitis A Virus Antibodies
If you have symptoms of an infection with or have been exposed to the hepatitis A virus; to detect previous infection or vaccination
A blood sample taken from a vein in your arm
How is the sample collected for testing?
A blood sample is taken by needle from a vein in the arm.
Is any test preparation needed to ensure the quality of the sample?
How is it used?
There are two kinds of antibody to the hepatitis A virus (HAV).
IgM (immunoglobulin M) is the first antibody produced by the body when it is exposed to a virus (remove glossary). This test is used to detect HAV infection in a patient with evidence of acute hepatitis, such as jaundice, dark urine, pale coloured stools, fever and loss of appetite. It appears two to three weeks after infection and has disappeared after two to four months.
IgG (immunoglobulin G) antibody develops later, continues to rise for several months and usually remains present for life, protecting the person against further infection by the same virus.
There is a specific test for HAV IgM antibody and a positive result is diagnostic of an existing HAV infection. There is no accepted test that is specific for HAV IgG antibody so a ‘total’ test that recognises both kinds of antibody is used. If the IgM test is negative, a positive test for total HAV antibodies is evidence of past infection or vaccination.
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, a total 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 total HAV antibody test can also be used to see if you have responded to the vaccine.
What does the test result mean?
If the total HAV test result is positive, the IgM antibody test is negative and you have not been given the HAV vaccine, you have had a hepatitis A infection in the past - even if you were not aware of it. 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.
Is there anything else I should know?
It is presumed that one infection with hepatitis A produces lasting immunity against further infections.
If a test is done after a vaccination and is negative it does not necessarily indicate the lack of immunity. This occurs because the lab assays do not detect low levels very reliably.
How could I have been infected with the virus without knowing it?
The virus is found in contaminated water and faeces. 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 poorly 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".
Is there any way to prevent the disease?
Can I perform this test at home?
No. The test is done by trained laboratory staff.