Hepatitis B is a viral infection of the liver which causes the organ to become inflamed and, in severe cases, to become damaged or even cease functioning. It is usually contracted through contact with the bodily fluids of an infected person. There are a number of different hepatitis B tests. In general, these tests can be divided into three categories: those which detect the virus, those which establish the severity of an infection, and those which monitor the liver for evidence of damage by the virus.
Some hepatitis B tests involve the examination of a sample of an individual’s blood for signs which suggest that the hepatitis B virus is present in his body. In one such test, the blood is studied for evidence of hepatitis B surface antigen (HBsAg), a substance which forms the outer layer of each hepatitis B particle. If HBsAg is found in an individual’s blood, it is likely he is infected with an active form of the hepatitis B virus which can be spread to others. Should HBsAg remain detectable in a test performed several months later, it is likely that the tested individual’s infection is chronic, or long-term, rather than acute, or short-term.
Another test examines the blood in search of antibodies which have developed in response to HBsAg. If these antibodies are present, it is likely that the tested individual has become immune to the hepatitis B virus. This immunity may have developed in response to a previous hepatitis B infection or may be the result of a vaccination.
Certain hepatitis B tests are intended to establish the severity of an infection. Such tests can give physicians information about how likely an infected individual is to infect others, and how well a treatment is working. One of these tests involves examining a blood sample for evidence of the protein hepatitis B e-antigen (HBeAg), which is generally present only during an active hepatitis B infection. If HBeAg is detected, it is likely that the tested individual is actively infected with hepatitis B, and is at risk of passing the infection to others.
A test which measures the amount of hepatitis B virus DNA (HBV DNA) in a blood sample is often used to determine how well a particular hepatitis B treatment is working. If HBV DNA measurements increase over time, it is likely that virus levels within the infected individual’s body are rising. This increase may suggest that the treatment currently being used to eliminate the virus is not working.
Finally, some hepatitis B tests monitor the liver for evidence of damage by the hepatitis B virus. For instance, a physician may analyze a blood sample to determine whether it contains substances that are normally processed by the liver. If such substances are present, the liver’s function may have been compromised by the effects of the hepatitis B virus.
Occasionally, a physician may analyze the effects of hepatitis B on the liver by ordering a biopsy. During a biopsy, a needle is inserted into the liver to draw out a very small amount of tissue. The tissue is then studied to determine how severely the liver has been damaged by the effects of the hepatitis B virus.
