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Screening and diagnosis
If you're pregnant, it's important to be checked for HBV early
in your pregnancy. Also, get tested if you have unprotected
sex with more than one partner, share needles when injecting
drugs or have spent time in an area where hepatitis B is
widespread.
People who adopt children from areas where hepatitis B is
common will want to have their children tested when they
arrive in the United States. Tests done in other countries may
not always be as reliable. To best meet the special needs of
adopted children, doctors usually make testing for HBV part of
a comprehensive health evaluation.
You and your children can be tested at your doctor's office, a
hospital or a public health clinic. Many public clinics offer
free testing for HBV and other sexually transmitted diseases.
Testing is important to protect you and your children and to
prevent transmission of the virus to others.
Diagnosis based on tests
Because many people with hepatitis B don't have signs and
symptoms, doctors diagnose the disease on the basis of one or
more blood tests. These tests include:
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Hepatitis B surface antigen (HBsAg).
Hepatitis B surface antigen is the outer surface of the virus.
Testing positive for this antigen means you can easily pass
the virus to others. A negative test means you're probably not
currently infected.
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Antibody to hepatitis B surface antigen (anti-HBs).
A positive result on this test means you have antibodies to
HBV. This may be due to a prior HBV infection from which
you've recovered. Or, you may already have been vaccinated. In
either case, you can't infect others or become infected
yourself because you're protected by the vaccine or your own
natural immunity.
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Antibody to hepatitis B core antigen (anti-HBc).
Although this test identifies people who have a chronic
infection, the results can sometimes be ambiguous. If you test
positive for hepatitis B core antibodies, you may have a
chronic infection that you can transmit to others. But you
also may be recovering from an acute infection or have a
slight immunity to HBV that can't otherwise be detected. How
this test is interpreted often depends on the results of the
other two tests. When the results are uncertain, you may need
to repeat all three tests.
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Additional tests
If you receive a diagnosis of hepatitis B, your doctor may
perform tests to check the severity of the HBV infection as
well as the health of your liver. These tests include:
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E-antigen test.
This blood test looks for the presence of a protein secreted
by HBV-infected cells. A positive result means you have high
levels of the virus in your blood and can easily infect
others. If the test is negative, you have lower blood levels
of HBV and are less likely to spread the infection.
Liver enzymes.
These blood tests check for elevated levels of liver enzymes
such as alanine aminotransferase and aspartate
aminotransferase, which leak into the bloodstream when liver
cells are injured.
Alpha-fetoprotein (AFP) test.
High blood levels of this protein may sometimes be a sign of
liver cancer.
Liver ultrasound or computerized tomography (CT) scan.
These tests look at the liver for complications such as liver
scarring (cirrhosis) or liver cancer.
Liver biopsy.
In this procedure, a small sample of liver tissue is removed
for microscopic analysis. A biopsy can accurately show the
extent of any liver damage and may help determine the best
treatment for you.
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