Hepatitis B infection is caused by the Hepatitis B Virus. Hepatitis B virus is spread by contact with contaminated blood and body fluids. Chronic infection with Hepatitis B virus results in damage to the liver, cirrhosis and/or liver cancer. The body’s immune system is responsible for the liver tissue damage because it destroys the liver cells containing the virus. Consumption of alcohol during infection with Hepatitis B virus is discouraged because it can increase the damage to the liver. Hepatitis B virus is prevented by cautious and safe handling of blood and body fluids, vaccination, and refraining from behavior known to be associated with acquisition of the virus. Serology testing to detect hepatitis B surface antigen (HBsAg) is the standard for diagnosing the disease.
In hepatitis B virus infection, surface antigen is detectable 2 – 5 weeks before onset of symptoms, rises in titer, and peaks at about the time of onset of clinical illness. Generally it persists for 1 – 5 months, declining in titer and disappearing with resolution of clinical symptoms. HBsAg is a first-line test for the diagnosis of acute or chronic hepatitis B. If positive, no other test is needed. HBsAg is an indicator for active infection. It is a marker used for detecting initial infection, monitoring the course of the infection, and progression to chronic disease. It is also used in the screening of donor blood.