Hepatitis A Virus Antibodies
A blood sample taken from a vein in your arm
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. 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. There is a specific test for HAV IgM antibody and a positive result is diagnostic of a current or recent HAV infection in the last six 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. It will also develop after vaccination. A positive HAV IgG is evidence of past infection or vaccination.
A total HAV antibody test recognises both HAV IgM and HAV IgG antibody. If the IgM test is negative, a positive test for total HAV antibodies is evidence of past infection or vaccination.
When is it requested?
A HAV IgG antibody or total HAV antibody can be done in some cases following exposure to this virus.
If you are being considered for the HAV vaccine, a HAV IgG antibody or total HAV 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 HAV IgG antibody or 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 HAV IgG antibody or total HAV antibody 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 have protection against HAV infection.
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?