Acute hepatitis is the initial infection, which most people recover from (thereby becoming immune). Symptoms of acute infection vary — the person could either be symptomless or be seriously ill. Fortunately, about 90% of healthy adults recover from an acute Hep B infection.
However, if the hepatitis virus remains in the bloodstream for over 6 months, it indicates chronic infection with Hepatitis B.
How can I test for Hepatitis B?
A blood test is all that is needed to diagnose a Hepatitis B infection. These are the three types of blood tests commonly used to diagnose Hepatitis B:
1). HBsAG: Hepatitis B Surface Antigen
An antigen is a foreign substance that triggers the immune systems to respond. (This response includes producing antibodies, which are proteins that identify and destroy antigens).
The surface antigen is a piece of the Hep B virus that can be found in an infected person’s blood. A positive HBsAG test means that the Hep B virus was found within the bloodstream. However, this is not enough to discern whether the infection is acute or chronic.
2). HbSAb, or anti-HBs (hepatitis B surface antibody)
Once formed, antibodies protect you from future infections by the same virus. The HbSAb test is done six months after a person recovers from an acute infection, or after successful response to the hepatitis B vaccine. A positive (also known as “reactive”) HbSAb test means that the person is now non-contagious and immune to Hepatitis B.
3). HbCAb, or anti-HBc (hepatitis B core antibody)
The core antibody is produced in response to the core antigen, which is another fragment of the hepatitis B virus. However, this antibody is found in chronically infected Hep B patients. Interpreting this test is more complicated. While it can indicate past or present infection, it can also be a false positive. Therefore, the HBcAb test needs to be done at least twice. If the Hep B core antibody appears together with the protective surface antibody (HBsAb), it means that the patient was previously infected and has since recovered. However, for chronically infected patients, the core antibody will appear together with the virus (a positive HBsAg test).
Written by: Sonia Lee, Hepatitis B Coalition Intern