Hepatitis A Testing
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 characterized by inflammation and enlargement of the liver. This test detects antibodies in the blood that are produced by the immune system in response to a hepatitis A infection.
Hepatitis A is one of five "hepatitis viruses" identified so far, including B, C, D, and E, that are known to cause the disease. While hepatitis A can cause a severe, acute disease that typically lasts 1 to 2 months, it does not cause a chronic infection as do some of the other hepatitis viruses.
Hepatitis A is spread, most commonly, from person-to person through stool (fecal) contamination or by ingesting food or water contaminated by the stool of an infected person (a foodborne illness). Recognized risk factors for hepatitis A include close contact with an infected person, international travel, household or personal contact with a child who attends a child care center, household or personal contact with a newly arriving international adoptee, a recognized foodborne outbreak, men who have sex with men, and use of illegal drugs.
Although there are many causes of hepatitis, the symptoms remain the same. In hepatitis, the liver is damaged and unable to function normally. It cannot process toxins or waste products such as bilirubin for their 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 panel can tell a health practitioner that someone has hepatitis, they do not identify the cause. Antibody tests for hepatitis viruses may help determine the cause.
There are two different classes of hepatitis A antibody that may be tested, IgM and IgG. When a person is exposed to hepatitis A, the body first produces hepatitis A IgM antibodies. These antibodies typically develop 2 to 3 weeks after first being infected (and are detectable before the onset of symptoms) and persist for about 3 to 6 months. Hepatitis A IgG antibodies are produced within 1 to 2 weeks of the IgM antibodies and usually persist for life.
- Because hepatitis A IgM antibodies develop early in the course of infection, a positive hepatitis A IgM test is usually considered diagnostic for a current or recent infection of hepatitis A. This test may be done as part of an acute viral hepatitis panel used to determine which virus is causing symptoms when viral hepatitis is suspected.
- An HAV IgG test may be used to help determine if a person has been infected in the past and has some immunity to the disease.
- A total hepatitis A antibody test detects the presence of both the IgM and IgG antibodies, thus can identify current and past infections.
A vaccine that prevents hepatitis A has been available since 1995. Historically, infection rates varied cyclically, with nationwide increases every 10-15 years. However, rates have declined in general since the vaccine was introduced. In 2010, the number of acute hepatitis A cases reported nationwide declined by approximately 53% from about 3,600 in 2006.
How is the sample collected for testing?
A blood sample is obtained by inserting a needle into a vein in the arm.
Is any test preparation needed to ensure the quality of the sample?
No test preparation is needed.
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 may be used to determine if the symptoms are due to hepatitis A.
A few different versions of the test may be used to detect different classes of hepatitis A antibodies.
- The HAV IgM antibody test detects the first antibody produced by the body when it is exposed to hepatitis A. This test is used to detect early or recent infections and to diagnose the disease in people with symptoms of acute hepatitis. It may be performed as part of an acute viral hepatitis panel.
- The HAV IgG test detects the IgG antibodies that develop later in the course of the disease. IgG antibodies remain present for many years, usually for life, providing protection against recurrent infection by the same virus. The IgG test is used to detect past HAV infections and may occasionally be used to determine if an individual has developed immunity from a previous infection (immune status), in which case a vaccine is not necessary.
- The total HAV antibody test detects both IgM and IgG antibodies and thus may be used to identify both current and past infections. This test will also be positive after receiving the vaccine, so sometimes it may be used to determine whether a person has developed immunity after vaccination, though this practice is not advised. Recommendations of the Advisory Committee on Immunization Practices (ACIP) state that "post-vaccination testing is not indicated because of the high rate of vaccine response among adults and children. In addition, not all testing methods approved for routine diagnostic use in the United States have the sensitivity to detect low anti-HAV concentrations after vaccination."
When is it ordered?
- Loss of appetite
- Nausea, vomiting, abdominal pain
- Dark urine and/or pale colored stool
- Joint pain
In some people and in many young children, hepatitis A may not cause any symptoms. Children infected by HAV often have very mild symptoms, such as fever and diarrhea, and are often thought to have "flu."
An HAV test may also be ordered when a person is likely to have been exposed to the virus regardless of whether symptoms are present or not.
What does the test result mean?
Results of hepatitis testing may indicate the following:
HAV IgM HAV IgG or Total Antibody (IgM and IgG) Results Indicate Positive Not Performed Acute or recent HAV infection Negative Positive No active infection but previous HAV exposure; has developed immunity to HAV or recently vaccinated for HAV Not Performed Positive Has been exposed to HAV but does not rule out acute infection Not Performed Negative No current or previous HAV infection; vaccine may be recommended if at risk
If the total antibody test or hepatitis A IgG result is positive and someone has never been vaccinated against HAV, then the person has had past exposure to the virus. About 30% of adults over age 40 have antibodies to hepatitis A.
Is there anything else I should know?
Hepatitis A vaccines are effective even when administered up to 15 days after exposure to the virus. Infants, immunocompromised people, people with chronic liver disease, or adults over 40 may be given an injection of immune globulin instead of the vaccine for post-exposure protection.
Although hepatitis A IgM antibodies are considered diagnostic for acute infection with hepatitis A, there has been increasing use of the test in people who do not have signs and symptoms of acute hepatitis. The Centers for Disease Control and Prevention have recommended that the test only be used for persons who clinically have acute hepatitis to decrease the possibility of falsely positive results.
How could I have gotten the virus without knowing it?
The virus is passed through contact with stool (fecal matter) from an infected person, typically via contaminated food or water. If a person infected with HAV does not wash their hands after using the bathroom, that person can pass the virus by handling raw fruits and vegetables consumed by others, or directly through person to person contact. You can also contract the virus by eating raw or improperly cooked seafood that had fed in contaminated waters. You may also contract the virus through sexual contact with someone who is infected but asymptomatic.
If I have hepatitis A, how long will I be contagious?
According to the World Health Organization, you can spread the disease to others roughly 1 to 3 weeks before symptoms, such as jaundice, begin to appear. Symptoms typically develop within 4 weeks but can appear any time between 2 and 6 weeks after you are first infected. You can continue to be contagious, but less so, for several weeks after jaundice develops.
How is hepatitis A treated?
There is no specific treatment for hepatitis A. Mild forms of the disease usually resolve on their own and leave no lasting damage to the liver. The focus is usually on supportive therapy, making sure you are getting enough fluids and nutrition by eating and drinking small amounts several times a day. In rare cases, fulminant hepatitis, a life-threatening form that causes liver failure, requires hospitalization. Hepatitis A tends to be more severe in the elderly and in those who also have chronic liver disease, so person with acute hepatitis A in those settings should be watched more closely.
Is there a way to prevent hepatitis A?
Yes. There is a vaccine available. It is recommended that all children be vaccinated at age one year. Any children ages 2-18 who did not receive the vaccine at age one should also receive the vaccine. It is also recommended for people who are at an increased risk of exposure to the virus, such as:
- People traveling to developing countries with a high rate of hepatitis A
- Illegal drug users
- Men who have sex with men
The vaccine is also recommended for those who are at a greater risk for complications from the disease, including people with chronic liver disease and those who have damage to their liver from some other cause.
If it is known that you were exposed to the hepatitis A virus, you may be given the vaccine to prevent the disease.
Hepatitis A can also be prevented with good hygiene. This includes washing hands well after using the bathroom, after changing diapers, and before eating or starting any food preparation.
If I have had a hepatitis A infection, can I get it again?
On This Site
Elsewhere On The Web
Centers for Disease Control and Prevention: Hepatitis A Information
American Liver Foundation: Hepatitis A
National Digestive Diseases Information Clearinghouse: What I need to know about Hepatitis A
FamilyDoctor.org: Hepatitis A