Definition
Hepatitis B is an inflammation of the liver caused by the hepatitis B virus and can cause chronic damage to the liver. “The test” for hepatitis B does not exist, there are many ways to determine whether an infection with hepatitis B is present. For example, the test for hepatitis B checks whether specific antibodies against the hepatitis B virus and/or virus components are present in the patient’s blood. Depending on which antibodies and how many or which components of the virus are found in the blood, laboratory physicians and doctors can determine whether the infection is recent or recent, or whether the patient has acquired the antibodies through vaccination.
What different tests are available?
There are various tests to detect infection with the hepatitis B virus in a patient:
- Antibody tests: Anti-HBc IgM and anti-HBc IgG antibodies are tested in the diagnosis of hepatitis B. These antibodies are directed against a protein from the virus core. IgM antibodies are produced at the beginning of the infection, their quantity decreases in the course of healing.
IgG antibodies are produced slightly later than IgM antibodies and remain detectable in the blood even after the hepatitis B infection has healed. They then indicate that a patient has been through hepatitis B. Other antibodies used in hepatitis B diagnostics are anti-HBe (against a protein produced during virus replication) and anti-HBs antibodies (against a surface protein).
These antibodies do not rise until several months after infection with hepatitis B and generally indicate (beginning) healing.
- Test for viral DNA: The genetic material of the hepatitis B virus consists of DNA. This DNA is detectable in the blood during an infection, about 2-4 weeks before other virus components and antibodies can be detected in the blood.
- Test for virus components: HBs-Ag (hepatitis B surface antigen), a component of the surface of the hepatitis B virus, is detectable in the blood. This virus component can usually be detected before symptoms begin.
Once the hepatitis B has healed, HBs-Ag is no longer detectable. If it is still found in the blood after 6 months, this is called a chronic hepatitis B infection. HBe-Ag (hepatitis B envelope antigen), a protein that is produced during virus replication, is also detectable.
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