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Chronic Hepatitis B

Chronic hepatitis B is an important preventable cause of cirrhosis and liver failure. It is estimated that 90-160,000 people in Australia have chronic hepatitis B. HBV-related hepatocellular carcinoma (HCC) is rising in frequency and is the third most common cause of cancer death in the Asia-Pacific region. Hepatitis B vaccination is the most important strategy to prevent chronic hepatitis B.

NATURAL HISTORY OF CHRONIC HEPATITIS B

HBV is a member of the hepadnavirus family, a family of hepatitis-causing DNA viruses, which use a RNA-dependent reverse transcriptase step in the replicative cycle.

Most patients with chronic hepatitis B contracted the infection in the first 3 years of life from maternal transmission or from intimate personal contact with an infected person in early childhood.

The natural history of infection acquired early in life appears to correspond to four distinct phases: immune tolerance, immune clearance, immune control and immune escape.

CHRONIC HBV INFECTION AND LIVER CANCER

Viral, host genetic and environmental factors are all important in hepatocarcinogenesis. However, the risk of HCC is greatest in the setting of cirrhosis (80% of cases) and active liver disease and viral replication.

Recent cross-sectional data from a large communitybased cohort in Taiwan, suggested a link between serum HBV-DNA levels and progression of liver disease and development of HCC. The therapeutic implications of these data are that cirrhosis and HCC risk may be reduced by effective antiviral therapy.

SEROLOGICAL TESTS IN HEPATITIS B

HBV has three major antigens, each of which induces an immune response. An appreciation of these responses is useful for the interpretation of serological data, for differentiating between acute and chronic infections, and for assessing which phase of infection a patient is in.