Hepatitis A Testing

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Also known as: HAV-Ab IgM; HAV-Ab IgG; HAV-Ab total
Formal name: Viral Hepatitis A Antibody
Related tests: Hepatitis B Testing; Hepatitis C Testing; Acute Viral Hepatitis Panel; Liver Panel; AST; ALT; ALP; Bilirubin

At a Glance

Why Get Tested?

To diagnose an infection with hepatitis A virus (HAV) or to evaluate the need for or response to the hepatitis A vaccine

When to Get Tested?

If you have symptoms of an infection with and/or have been exposed to HAV; if you have chronic liver disease; or if you have received the HAV vaccine

Sample Required?

A blood sample drawn from a vein in your arm

Test Preparation Needed?

None

The Test Sample

What is being tested?

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. Hepatitis A is one of five "hepatitis viruses" identified so far, including B, C, D, and E that are known to cause the disease.

Hepatitis A is spread through food or water contaminated with the virus or by coming in contact with an infected person. While hepatitis A can cause a severe, acute disease, it does not cause a chronic infection as do some of the other hepatitis viruses. If you are exposed to hepatitis A, your immune system produces antibodies in response to the virus. This test detects hepatitis A antibodies in the blood.

While hepatitis has many different causes, the signs and the symptoms are 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 your doctor that you have hepatitis, they will not tell her what is causing it. Antibody tests for hepatitis viruses may help determine the cause.

If you are exposed to hepatitis A, your body will first produce hepatitis A IgM antibodies. These antibodies typically develop 2 to 3 weeks after first being infected and persist for about 2 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 acute hepatitis A. A total hepatitis A antibody test detects the presence of the IgM and IgG antibodies and may help determine if you have been infected in the past and have some immunity to the disease. A test for hepatitis A IgM may be part of an acute viral hepatitis panel that may be used to determine which virus is causing symptoms when viral hepatitis is suspected.

A vaccine is available to help prevent hepatitis A. According to the CDC, cases of hepatitis A have dropped by 89% since the introduction of the hepatitis A vaccine in 1995. In 2007, just under 3000 cases of acute hepatitis A were reported, the lowest to date.

How is the sample collected for testing?

A blood sample is obtained by inserting a needle into 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?

No test preparation is needed.

The Test

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 antibodies.

  • Hepatitis A IgM 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 acute hepatitis.
  • Hepatitis A IgG 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 vaccine.

An hepatitis A antibody test may be used to screen for exposure in those who are asymptomatic.

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 IgM antibodies to hepatitis A is done when you have acute 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 vaccine, 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 vaccine, 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 IgM and IgG 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 acute infection with hepatitis A, there has been increasing use of the test in persons who do not have signs and symptoms 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 falsely positive results.

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Common Questions

1.  How could I have gotten the virus without knowing it?

The virus is found in contaminated water and feces. 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 improperly 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 diarrhea, and are often thought to have "flu."

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2.  If I have hepatitis A, how long will I be contagious?

You can spread the disease to others from the time you are first infected up until symptoms begin to appear, which can be about 4 weeks. Generally, adults are contagious for 2 weeks after contracting the disease. However, children and individuals who are immunocompromised may be contagious for up to 6 months.

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3.  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 older persons and in those who also have chronic liver disease, so person with acute hepatitis A in those settings will be watched more closely.

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4.  Is there a way to prevent hepatitis A?

Yes. There is a vaccine available. It is recommended for all children at age 1 year and for those who are at an increased risk of exposure to the virus such as:

  • children or adolescents from 2-18 years old who live in parts of the United States where hepatitis A is common
  • 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.

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Article Sources

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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.

Sources Used in Current Review

(Update August 21, 2009) Lehrer J. Hepatitis A. MedlinePlus Medical Encyclopedia. Available online at http://www.nlm.nih.gov/medlineplus/ency/article/000278.htm. Accessed August 2009.

(Updated June 13, 2008) Centers for Disease Control and Prevention. FAQs for Health Professionals, Hepatitis A. Available online at http://www.cdc.gov/hepatitis/HAV/HAVfaq.htm#general through http://www.cdc.gov. Accessed August 2009.

(June 24, 2008) CDC. Statistics and Surveillance, Hepatitis A. Available online at http://www.cdc.gov/hepatitis/Statistics.htm through http://www.cdc.gov. Accessed September 2009.

(Sep. 5, 2009) Mayo Clinic Staff. Hepatitis A. Available online at http://www.mayoclinic.com/health/hepatitis-a/DS00397 through http://www.mayoclinic.com. Accessed September 2009.

Forbes BA, Sahm DF, Weissfeld AS. Bailey & Scott's Diagnostic Microbiology 12th Edition: Mosby Elevier, St. Louis, MO; 2007, Pp 764-765.

(Updated February 2009) American Academy of Family Physicians. Hepatitis A. Available online at http://familydoctor.org/online/famdocen/home/common/infections/hepatitis/897.html through http://familydoctor.org. Accessed August 2009.

Tietz Textbook of Clinical Chemistry and Molecular Diagnostics. Burtis CA, Ashwood ER and Bruns DE, eds. 4th ed. St. Louis, Missouri: Elsevier Saunders; 2006, Pp 1804-1805.

Henry's Clinical Diagnosis and Management by Laboratory Methods. 21st ed. McPherson RA and Pincus MR, eds. Philadelphia: 2007, Pp 271.

Sources Used in Previous Reviews

Clinical Chemistry: Principles, Procedures, Correlations. Michael L. Bishop, Janet L. Duben-Engelkirk, Edward P. Fody. Lipincott Williams & Wilkins, 4th Edition.