Hepatitis B is diagnosed by testing for various antigens and antibodies (see table below). The main markers are anti-HBc antibody and HBs antigen. If an HBs-Ag test is positive, further tests should be done to establish the hepatitis activity. These tests are HBe-Ag and anti-HBe assays and direct measurement of the amount of virus DNA in the blood (viral load).

Liver function tests (ALT, AST) are of limited value in indicating the inflammatory activity associated with hepatitis. The disease activity and connective tissue reaction in the liver can be evaluated reliably only by investigating a sample of liver tissue. Non-invasive procedures such as elastography give an indirect indication of the degree of fibrosis.

Since people with chronic hepatitis B are at greater risk of developing liver cancer, alpha-fetoprotein (AFP), a tumour marker for liver cancer, should be monitored and ultrasound scans of the liver should be done at half-yearly intervals.

Antigens (Ag) are substances which the body identifies as foreign (e.g. virus components) and which lead to the production of antibodies (Ab).

In order to estimate the extent of connective tissue infiltration and inflammatory activity in the liver – for example, as a basis for deciding on treatment – liver biopsy is recommended. Biopsy of the liver involves the removal of a small piece of tissue (under local anaesthesia) for histological examination under a microscope. Another liver biopsy after completion of treatment may be indicated in order to assess the response to treatment. Non-invasive procedures (laboratory markers, elastography) are fairly reliable predictors of cirrhosis even in the absence of liver biopsy.