How is it used?
This test is used to help diagnose a liver infection due to the hepatitis A virus (HAV). There are several causes of
hepatitis and the accompanying symptoms, so this test is used to determine if your symptoms are due to hepatitis A.
There are two versions of the test, and these are used detect two different types of hepatitis A .
- Hepatitis A is the first antibody produced by the body when it is exposed to hepatitis A. The hepatitis A IgM test is used to screen for early detection of infection and is used to diagnose the disease in a patients with evidence of hepatitis.
- Hepatitis A antibodies develop later and remain present for many years, usually for life, and protect you against further infection by the same virus. There is no test specifically for hepatitis A IgG antibodies; a total antibody test (which detects both IgM and IgG antibodies) detects both current and previous infection with hepatitis A and will also be positive after receiving the hepatitis A .
An hepatitis A antibody test may be used to screen for exposure in those who are .
This test may also be used to determine if you have produced antibodies and developed immunity in response to a hepatitis A vaccine or a previous hepatitis A infection.
In acute hepatitis, other tests such as bilirubin, liver panel, ALT, and AST may be performed to help diagnose the condition.
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When is it ordered?
Testing for the presence of antibodies to hepatitis A is done when you have symptoms such as:
- Fever
- Fatigue
- Loss of appetite
- Nausea, vomiting, abdominal pain
- Dark urine and/or pale colored stool
- Joint pain
- Jaundice
In some people and in many young children, hepatitis A may not cause any symptoms. This test may also be done when you are likely to have been exposed to the virus regardless of symptoms.
If you are being considered for the hepatitis A , a total antibody test may be ordered 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 hepatitis antibody test can also be used to see if you have responded to the vaccine and developed immunity. Because almost all people respond to the vaccine, this is not usually done.
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What does the test result mean?
If you have not been given the hepatitis , results of hepatitis testing indicates the following:
| HAV IgM |
Total HAV Antibody (IgM and IgG) |
Results Indicate |
| Positive |
|
Acute HAV infection |
| Negative |
Positive |
No active infection, but previous HAV exposure; has developed immunity to HAV |
| |
Positive |
Has been exposed to HAV but does not rule out acute infection |
| |
Negative |
No current or previous HAV infection; vaccine may be recommended if at risk |
A total antibody test detects both and antibodies but does not distinguish between them.
If the total antibody test or hepatitis A IgG result is positive and you have not gotten the hepatitis A vaccine, you have had a hepatitis A infection, even if you were not aware of it. About 30% of adults over age 40 have antibodies to hepatitis A.
If you have been given the vaccine, a positive result means you are immune to hepatitis A and generally cannot be reinfected by it.
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Is there anything else I should know?
In the past, the only way to prevent you from developing hepatitis A after it was known that you were exposed to the virus was to give you an injection of immune globulin. In June 2007, guidelines in the United States were changed to recommend that you be given the hepatitis A vaccine after exposure if you are 40 years old or younger. Not enough is known about the effectiveness of the vaccine in age groups older than this so if you are 40 or older, you may be given immune globulin after exposure.
Although hepatitis A IgM antibodies are considered diagnostic for infection with hepatitis A, there has been increasing use of the test in persons who do not have and of acute hepatitis. The Centers for Disease Control and Prevention (CDC) have recommended that the test only be used in persons who clinically have acute hepatitis to prevent results.
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