A diagnosis of hepatitis B might involve medical screening, several blood tests, or possibly a liver biopsy. Hepatitis B is a highly contagious liver infection that can potentially be fatal. If a person is considered to be high risk for the disease, he or she might undergo screening even without experiencing any symptoms. Also, there are many blood tests that can be done which typically check for hepatitis B antigens or DNA, and the results can usually determine whether an acute or chronic infection is present. In cases where a doctor suspects a chronic infection, he might recommend a liver biopsy to confirm the diagnosis of hepatitis B.
A person can contract a hepatitis B infection through direct contact with contaminated blood or body fluids, such as through sexual contact, using injection drugs, or giving birth. The disease primarily infects the liver, and it can lead to serious conditions such as cirrhosis or liver cancer. In severe cases, it can even be fatal, and about 1 million people worldwide die annually from a hepatitis B infection. Symptoms include jaundice, nausea, fatigue, and muscle or joint pain. Many times, a person who has a chronic infection does not experience any symptoms, so a diagnosis of hepatitis B is important for keeping the disease from spreading to others.
A doctor might first recommend a medical screening for a person who is at high risk for hepatitis B. A high risk individual is one who has had sex with multiple partners or with someone who is infected with the virus, uses injection drugs, lives in regions where hepatitis B is common, or was born to a mother with the infection. The screening usually entails a complete medical history and physical exam. After the screening, the doctor might recommend a lifestyle change, various treatments, or performing blood tests for a diagnosis of hepatitis B.
There are several different types of blood tests that can be used to make a diagnosis of hepatitis B. One is a hepatitis B surface antigen test (HBsAg) that looks for the outer surface of the virus cells. The antigens appear about four weeks after one is exposed to the virus and are cleared out of the body around four months after the onset of symptoms. If the body does not eradicate the antigens after a six-month period, it generally means the infection has become chronic. A positive test result indicates an active infection that is easily spread to others.
Similarly, the hepatitis B e antigen test (HBeAg) checks for a particular protein that is released by the virus when it is multiplying. If the test is positive for e antigens, it means there is a large amount of virus cells. It also can mean there is a high risk of the infection spreading to others.
Another blood test a doctor might perform for a diagnosis of hepatitis B is a hepatitis DNA test, which shows the amount of hepatitis virus DNA present in the blood. With an acute infection, the DNA shows up soon after exposure but disappears once the infection has passed. If the hepatitis DNA exists for several months, it suggests a chronic infection.
In cases when a diagnosis of hepatitis B is made for a chronic infection, a doctor might also recommend having a liver biopsy done. The biopsy procedure involves collecting a tissue sample from the liver by using a long, thin needle through the skin. The tissue is then examined under a microscope to see how much damage has already been done to the liver from cirrhosis or inflammation.