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  Back Blood-tests Explained


Hepatitis B


At a Glance

Why Get Tested?

To screen for or diagnose a hepatitis B virus (HBV) infection or to determine if the vaccine against hepatitis B has produced the desired level of immunity; may also be used to guide treatment and assess its effectiveness

When to Get Tested?

When you have risk factors for HBV infection or when you have signs and symptoms of acute hepatitis; when you have a condition that requires chemotherapy or drugs that suppress your immune system and you might have been exposed to HBV in the past; when you are being treated for HBV

Sample Required?

A blood sample drawn from a vein in your arm

Test Preparation Needed?

None

The Test Sample

What is being tested?

Hepatitis B tests detect substances that reflect a current or previous infection with hepatitis B virus (HBV). Some tests detect viral proteins (antigens) or the antibodies that are produced in response to an infection, while other types of tests detect or evaluate the genetic material (DNA) of the virus. The pattern of test results can identify a person who has a current active infection or one who has immunity as a result of previous exposure.

For details on the various tests, see the table under "How is it used?"

Hepatitis is a condition characterized by inflammation and enlargement of the liver. It has several various causes, one of which is infection by a virus. HBV is one of five "hepatitis viruses" identified so far that are known to mainly infect the liver. The other four are hepatitis A, hepatitis C, hepatitis D, and hepatitis E.

HBV is spread through contact with blood or other body fluids from an infected person. Exposure can occur, for example, through sharing of needles for IV drug use or through unprotected sex. People who live in or travel to areas of the world where hepatitis B is prevalent are at a greater risk. Rarely, mothers can pass the infection to their babies, usually during or after birth. The virus is not spread through casual contact such as holding hands, coughing or sneezing. However, the virus can survive outside the body for up to seven days, including in dried blood, and can be passed by sharing items such as razors or toothbrushes with an infected person.

Effective hepatitis B vaccines have been available in the U.S. since 1981, and beginning in 1991, health care providers in the U.S. began vaccinating infants at birth. Still, the Centers for Disease Control and Prevention (CDC) estimates that between 804,000 and 1.4 million people in the U.S. are infected with the virus, most of whom are not aware that they are infected.

The course of HBV infections can vary from a mild form that lasts only a few weeks to a more serious chronic form lasting years. Sometimes chronic HBV leads to serious complications such as cirrhosis or liver cancer. Some of the various stages or forms of hepatitis B include:

  • Acute infection — presence of typical signs and symptoms with a positive screening test
  • Chronic infection — persistent infection with the virus detected by laboratory tests accompanied by inflammation of the liver
  • Carrier (inactive) state — persistent infection but no liver inflammation (a carrier is someone who may appear to be in good health but harbors the virus and can potentially infect others)
  • "Cleared" infection — no longer has any evidence of infection; viral antigen and DNA tests are negative and no signs or symptoms of liver inflammation (although, in many cases, the virus is present in an inactive state in the liver)
  • Reactivation — return of HBV infection with liver damage in a person who was a carrier or who had "cleared" infection; this most commonly occurs in persons treated with chemotherapy for cancer or with drugs that suppress the immune system used to treat autoimmune diseases or following an organ transplant.

Though a potentially serious infection, acute HBV infection usually resolves on its own in most adults. Infants and children tend to develop a chronic infection more often than adults. Approximately 90% of infants infected with HBV will develop a chronic condition. For children between the ages of one and five, the risk of developing chronic hepatitis drops to between 25% and 50%. Over the age of five, only 6% to 10% of HBV infections become chronic.

The vast majority of those with chronic infections will have no symptoms. For acute infections, the symptoms are very similar to those of other types of acute hepatitis. Symptoms include fever, fatigue, nausea, vomiting, and jaundice. With acute hepatitis, the liver is damaged and is not able to function normally. It may not process toxins or waste products such as bilirubin for their removal from the body. During the course of disease, bilirubin and liver enzyme levels in the blood may increase. While tests such as bilirubin or a liver panel can tell a health practitioner that someone has hepatitis, they will not indicate what is causing it. Tests that detect infection with a hepatitis virus may help determine the cause.

Hepatitis B testing can be used to screen for infection in the absence of symptoms, to determine whether infection is acute or chronic, or to monitor a chronic infection and the effectiveness of treatment. Initial testing may include the following, often performed together as a panel of tests:

  • Hepatitis B surface antigen
  • Hepatitis B surface antibody
  • Total hepatitis B core antibody (IgM and IgG)

Additional or follow-up testing may include:

  • IgM antibody to hepatitis B core antigen
  • Hepatitis B e-antigen
  • Anti-hepatitis B e antibody
  • Hepatitis B viral DNA
  • Hepatitis B genotyping

Two tests, hepatitis B surface Ag and hepatitis B core antibody, IgM, may be performed as part of an acute viral hepatitis panel.

How is the sample collected for testing?

A blood sample is drawn by needle from a vein in the arm.

Is any test preparation needed to ensure the quality of the sample?

No test preparation is needed.

The Test

How is it used?

Hepatitis B virus (HBV) tests may be used for a variety of reasons. Some of the tests detect antibodies produced in response to HBV infection; some detect antigens produced by the virus, and others detect viral DNA.

The main uses for HBV tests include:

  • To determine whether acute signs and symptoms are due to HBV infection; two tests, hepatitis B surface Ag and hepatitis B core antibody IgM, may be performed as part of an acute viral hepatitis panel along with tests for hepatitis A (HAV) and hepatitis C (HCV) to determine which virus may be causing the infection.
  • To diagnose chronic HBV hepatitis
  • To monitor chronic hepatitis B infection and its treatment
  • To detect previous exposure to hepatitis B, in a person who is immune compromised (when the virus can become reactivated)

Some of the secondary reasons to perform testing include: to screen for hepatitis B infection in at-risk populations or in blood donors, to determine if someone is a carrier, to detect previous infection (with subsequent immunity), and to determine if immunity has developed due to vaccination.

Generally, one set of tests is used as an initial panel of tests to detect HBV infection or to determine the cause of acute symptoms while another set of tests may be used after a diagnosis is made to monitor possible progression of the disease, to detect chronic infection, and/or to determine carrier status.

The following table summarizes the set of tests typically used for initial testing:

Test Description Use and Comments
Hepatitis B surface antigen (HBsAG) Detects protein that is present on the surface of the virus To screen for, detect, and help diagnose acute and chronic HBV infections; earliest routine indicator of acute hepatitis B and frequently identifies infected people before symptoms appear; undetectable in the blood during the recovery period; it is the primary way of identifying those with chronic infections, including "HBV carrier" state.
Hepatitis B surface antibody (anti-HBs) Detects antibody produced in response to HBV surface antigen Used to detect previous exposure to HBV; it can also develop from successful vaccination so it is used to determine the need for vaccination (if anti-HBs is absent) or to determine if a person has recovered from an infection and is immune (cannot get the infection again).
Total anti-hepatitis B core (anti-HBc, IgM and IgG) Detects both IgM and IgG antibodies to hepatitis B core antigen Can be used to help detect acute and chronic HBV infections; the IgM antibody is the first antibody produced after infection with HBV; IgG antibody is produced in response to the core antigen later in the course of the infection and usually persists for life.

The following table summarizes tests that may be used as follow-up after initial tests detect an HBV infection:

Test Description Use and Comments
Anti-hepatitis B core (anti-HBc), IgM Detects only the IgM antibody to the hepatitis B core antigen Used to detect acute infections; sometimes present in chronic infections as well
Hepatitis B e-antigen (HBeAG) Detects protein produced and released into the blood Often used as a marker of ability to spread the virus to other people (infectivity); it may also be used to monitor the effectiveness of treatment. However, there are some types (strains) of HBV that do not make e-antigen; these are especially common in the Middle East and Asia. In areas where these strains of HBV are common, testing for HBeAg is not very useful to determine whether the virus can be spread to others.
Anti-hepatitis B e antibody (Anti-HBe) Detects antibody produced by the body in response to the hepatitis B "e" antigen Used to monitor acute infections in those who have recovered from acute hepatitis B infection; anti-HBe will be present along with anti-HBc and anti-HBs.
Hepatitis B viral DNA Detects hepatitis B viral genetic material in the blood A positive test indicates that the virus is multiplying in a person's body and that person is highly contagious. The test is often used to monitor the effectiveness of antiviral therapy in people with chronic HBV infections.
Hepatitis B virus resistance mutations Detects mutations in the particular virus causing a person's infection that allows the virus to be resistant to treatments (reverse transcriptase inhibitors) Helps to select appropriate treatment, especially in people who have been treated previously or in those who are not responding to treatment

While the tests described above are specific for HBV, other liver tests such as AST, ALT, and gamma-glutamyl transferase (GGT) may be used to monitor the progress of the disease. In some cases, a liver biopsy may be performed to evaluate how much damage has occurred to the liver.

When is it ordered?

Hepatitis B tests may be ordered when someone has signs and symptoms associated with acute hepatitis to determine if they are due to infection with HBV. Some of these include:

  • Fever
  • Fatigue
  • Loss of appetite
  • Nausea, vomiting
  • Abdominal pain
  • Dark urine
  • Pale stools
  • Joint pain
  • Jaundice

Hepatitis B tests may be done as follow up when routine tests results such as ALT and/or AST are elevated. Sometimes acute forms of hepatitis may be detected this way since they may cause only mild symptoms that can be confused with the flu. Chronic hepatitis more often has no symptoms and is more commonly detected when routine test results are abnormal.

A test for hepatitis B surface antigen (HBsAg) may be used for screening when someone falls into one of the high risk categories for chronic hepatitis B. In September 2008, the Centers for Disease Control and Prevention (CDC) revised its guidelines and recommends the following groups be tested for HBsAg:

  • Healthcare and public safety workers
  • People born in areas of the world that have a greater than 2% prevalence of HbsAg (for example, much of Asia and Africa)
  • People born in the U.S. but who were not vaccinated and whose parents are from an area with greater than 8% prevalence of HbsAg
  • Men who have sex with men
  • People who have elevated liver enzymes (ALT and AST) with no known cause
  • People with certain medical conditions that require that their immune system be suppressed, such as organ transplant recipients
  • Pregnant women
  • People who are in close contact with someone infected with HBV
  • Those infected with HIV

When hepatitis B tests are used to monitor people with chronic hepatitis B infections, they may be performed on a regular basis. Hepatitis B surface antigen (HBsAg) and hepatitis B e antigen (HBeAg) are usually measured about every 6 months to a year since, in some people, HBeAg (and, less commonly, HBsAg) will go away on their own. In those who are being treated for chronic HBV, HBeAg and HBV DNA tests can be used to determine whether the treatment is successful.

What does the test result mean?

The tests for hepatitis B may be ordered individually but are often ordered in some combination, depending on the reason for testing. Results of the tests are typically evaluated together. Sometimes the meaning of one result depends on the result of another test. However, not all tests are performed for all people.

The table below summarizes possible interpretations of some common patterns of results.

Initial Tests     Follow-up Tests        
Hep B surface antigen (HBsAg) Hep B surface antibody (Anti-HBs) Hep B core antibody Total (Anti-HBc IgG+IgM) Hep B core antibody (Anti-HBc IgM) Hep B e antigen (HBeAg)* Hep B e antibody (Anti-HBe) HBV DNA Possible Interpretation / Stage of Infection
Negative Negative Negative Not performed Not performed Not performed Not performed No active or prior infection; not immune — may be good candidate for vaccine; possibly in the incubation stage
Negative Positive Negative Not performed Not performed Not performed Not performed Immunity due to vaccination
Negative Positive Positive Not performed Not performed Not performed Not performed Infection resolved (recovery), virus cleared; immunity due to natural infection. However, if immunosuppressed, virus can reactivate.
Positive Negative Positive or Negative Positive or Negative Positive Negative Detected or none detected Acute infection, usually with symptoms; contagious; could also be flare of chronic infection
Negative Negative Positive Positive Negative* Positive None detected Acute infection is resolving (convalescent)
Positive Negative Positive Negative Positive Negative Detected Usually indicates an active chronic infection (liver damage likely)
Positive Negative Positive Negative Negative* Positive None detected or detected at very low level Chronic infection but low risk of liver damage — carrier state

*Note: There are some types (strains) of HBV that do not make e-antigen. In areas where these strains of HBV are common (in the Middle East and Asia), testing for HBeAg is not very useful. In these cases, a negative HbeAg result does not necessarily mean that the antigen is not present or that the person is not infectious; it may be that the person is infected with a strain that does not make the e-antigen.

Monitoring treatment of chronic infection: If the results from initial and follow-up testing indicate that a person has chronic hepatitis B, then the individual may be treated with medication and the effectiveness of that treatment may be monitored using the tests for HBe antigen and antibody and HBV DNA:

  • If HBeAg becomes negative and anti-HBe becomes positive during treatment, this usually indicates that it is effective and that treatment can be discontinued after an additional 6-12 months.
  • HBV DNA measures the amount of virus present in the blood. A high result usually means that the virus is actively replicating and that treatment is not effective. A low result or one that is reported as below a lower limit (none detected) means the virus is not present or is present in such low numbers that it cannot be detected. This usually indicates that the therapy is effective.

Is there anything else I should know?

Even if you don't have symptoms, an HBV infection can damage your liver and you can spread the infection to others. For this reason, it is important to get tested if you think you have been exposed to HBV.

Blood banks screen all donated blood for the hepatitis B virus (HBV DNA), hepatitis B surface antigen (HbSAg), and hepatitis B core antibody (anti-HBc). Donors are notified of any confirmed positive reactions. People who receive a notice regarding possible infection with hepatitis B after donating should visit their health care provider for further testing. The health practitioner will order additional tests to make a proper diagnosis and determine if treatment is necessary.

If exposed to HBV, an infection can be avoided by getting a shot of hepatitis B immune globulin (HBIG) within 24 hours.

A test is available to determine the specific type (strain) of hepatitis B virus that is causing a person's infection. This is called HBV genotyping. However, this testing is currently mainly used in research settings and not for clinical purposes.

Hepatitis D (HDV) is another virus that can cause liver infections, but only if hepatits B is also present. A person may become infected with both viruses at the same time (a co-infection) or may first be infected with hepatitis B and then become infected with HDV (a superinfection). In the U.S., the incidence of HDV is low. There is no vaccine for HDV, but since it causes infections only in the presence of HBV, it may be prevented with the HBV vaccine.



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