Seroprevalence of Hepatitis B Surface Antigen Among Voluntary Blood Donors Over a Five-Year Period

Abstract

Hepatitis B surface antigen (HBsAg) is the oldest and most widely used marker for keeping infectious units out of the blood supply, and the proportion of donors who test positive is often quoted as a measure of how safe a blood service is. This narrative review asks what such a figure can and cannot tell a reader. It draws on published work on the virus and its natural history, on the global pattern of infection and its link to age at infection, on donor selection and screening strategies, and on the performance of HBsAg assays, and it reports no donor data of its own. HBsAg positivity among donors reflects the community the donors come from, the way they are recruited and deferred, the assay used and the point in infection at which they happen to give blood. Window-period and occult infections are invisible to HBsAg testing, so a low figure is not proof that the supply is free of risk, and a high one does not by itself identify which donors or settings are to blame. Comparisons between services are weakened by differences in donor type, first-time and repeat donation, and reporting. The review concludes that donor HBsAg figures are best read as a description of screening yield in one setting and period, and it sets out what a transparent report of such figures should contain.