Hepatitis B Blood Tests: FAQ
There is a simple hepatitis B blood test that your doctor or health clinic can order called the “hepatitis B blood panel”. This blood sample can be taken in the doctor’s office. There are 3 common tests that make up this blood panel. Sometimes the doctor may ask to check your blood again six months after your first visit to confirm your hepatitis B status. If you think you have been recently infected with hepatitis B, it will take 4 -6 weeks before the virus will be detected in your blood.
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? In addition, it is helpful if you request a written copy of your blood tests so that you fully understand which tests are positive or negative.
The hepatitis B blood panel requires only one blood sample but includes three tests:
- HBsAg (hepatitis B surface antigen)
- HBsAb or Anti-HBs (hepatitis B surface antibody)
- HBcAb or anti-HBc (hepatitis B core antibody)
The doctor needs all 3 blood test results in order to determine your diagnosis.
This tests for the presence of virus. A "positive" or "reactive" HBsAg test result means that the person is infected with the hepatitis B virus, which can be an "acute" or a "chronic" infection. Infected people can pass the virus on to others through their blood and infected bodily fluids.
A "positive" or "reactive" HBsAb (or anti-HBs) test result indicates that a person has successfully responded to the hepatitis B vaccine or has recovered from an acute hepatitis B infection. This result means that you are immune to future hepatitis B infection and you are not contagious. This test is not routinely included in blood bank screenings.
What is the hepatitis B core antibody (HBcAb)?
The HBcAb is an antibody that is part of the virus- it does not provide protection. 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 results of the other two tests. 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).
First, do not panic. The letter does not necessarily mean
that you are infected with hepatitis B.
All donated blood is screened for hepatitis B. Many blood banks use the "hepatitis B core antibody" test to screen donor blood for potential hepatitis B infection (see “What is the hepatitis B core antibody?” above). This test can detect whether a person might have been exposed to the hepatitis B virus, but by itself this blood test doesn't tell whether the person is actually infected or not. This is why it is very important to see your doctor so that he can order the hepatitis B blood panel to make an accurate diagnosis.