Hepatitis A Virus Antibodies
At a Glance
Why Get Tested?
To diagnose an infection with hepatitis A virus, or to find out the need for or the response to hepatitis A vaccination
When to Get Tested?
If you have symptoms of an infection with or have been exposed to the hepatitis A virus; to detect previous infection or vaccination
Sample Required?
A blood sample taken from a vein in your arm
Test Preparation Needed?
None required
The Test Sample
What is being tested?
Hepatitis A antibodies are produced in response to an infection with the hepatitis A virus. The test detects the presence of this antibody.
How is the sample collected for testing?
A blood sample is taken by needle from a vein in the arm.
NOTE: If undergoing medical tests makes you or someone you care for anxious, embarrassed, or even difficult to manage, you might consider reading one or more of the following articles: Coping with Test Pain, Discomfort, and Anxiety, Tips on Blood Testing, Tips to Help Children through Their Medical Tests, and Tips to Help the Elderly through Their Medical Tests.
Another article, Follow That Sample, provides a glimpse at the collection and processing of a blood sample and throat culture.
Is any test preparation needed to ensure the quality of the sample?
None required
The Test
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.
Common Questions
Ask a Laboratory Scientist
Article Sources
NOTE: This article is based on research that utilizes the sources cited here as well as the collective experience of the Lab Tests Online Editorial Review Board. This article is periodically reviewed by the Editorial Board and may be updated as a result of the review. Any new sources cited will be added to the list and distinguished from the original sources used.
