Hepatitis B antigen screening in South Australian and Northern Territory blood donors.

A standard counterelectrophoresis method has been used to screen almost 250,000 samples from South Australian and Northern Territory blood donors since 1971. The initial incidence of approximately one hepatitis B antigen positive donor per thousand has diminished as these donors have been excluded from further blood donation. There is a predominance of males in the series, and more of the hepatitis B antigen carriers are in the younger age groups than expected. A higher than expected incidence of hepatitis B antigen positives has been noted in Northern Territory donors. Follow-up of donors found to be hepatitis B antigen positive has shown that the majority remain positive for more than two years without developing overt hepatitis. These individuals may represent a long-term asymptomatic carrier state.