Blood Tests

Be sure to carefully discuss your blood test results with your health care provider. Understanding your hepatitis B blood test results can be confusing, so you want to be clear about your diagnosis - do you have a new infection, have you recovered from a past infection, or do you have a chronic infection?

You may want to take a copy of this information with you to your appointment to use as a reference guide. In addition, it is helpful if you request a written copy of your blood tests so that you fully understand which test is positive or negative.

To understand your tests, you will need to understand two basic medical terms:

Antigen -a foreign substance in the body, such as the hepatitis B virus.
Antibody -a protein that your immune system makes in response to a foreign substance. Antibodies can be produced in response to a vaccine or a natural infection. Antibodies usually protect you from future infection.

Common Hepatitis B Blood Tests

HBsAg (hepatitis B surface antigen) - This refers to the outer surface of the hepatitis B virus that triggers an antibody response. A "positive" or "reactive" HBsAg test result means that the person is infected with the hepatitis B virus. This can be an "acute" or a "chronic" infection. Infected people can pass the virus on to others through their blood.
HBsAb or anti-HBs (hepatitis B surface antibody) - This refers to the protective antibody that is produced in response to an infection. It appears when a person has recovered from an acute infection and cleared the virus (usually within six months) or responded successfully to the hepatitis B vaccine shots. A "positive" or "reactive" HBsAb (or anti-HBs) test result indicates that a person is "immune" to any future hepatitis B infection and is no longer contagious. This test is not routinely included in blood bank screenings.
HBcAb or anti-HBc (hepatitis B core antibody) - This refers to an antibody that is produced in response to the core-antigen, a component of the hepatitis B virus. However, this is not a protective antibody. In fact, it is usually present in those chronically infected with hepatitis B. A "positive" or "reactive" HBcAb (or anti-HBc) test result indicates a past or present infection, but it could also be a false positive. The interpretation of this test result depends on the first two test results. Its appearance with the protective surface antibody (positive HBsAb or anti-HBs) indicates prior infection and recovery. For chronically infected persons, it will usually appear with the virus (positive HbsAg).