Present and future trends in the laboratory diagnosis of viral hepatitis.

The development of sensitive, specific, serological techniques for the detection of hepatitis B surface antigen (HBsAg) has resulted in the clarification of diverse aspects of the epidemiology of hepatitis type B. It is also provided a means whereby blood donors, potentially infected with the heaptitis B virus, may be screened out of the blood donating population, thus reducing the risk of transmitting hepatitis type B through the administration of blood and blood products. Immunoelectro-osmophoresis (IEOP) has been the most widely used technique for the large-scale testing of samples for HBsAg, such as required in blood transfusion centres. However, it has become increasingly evident that a considerable number of infectious units of blood are not detected by this method. Consequently, more sensitive techniques have been developed. Among these, the most promising are the reverse passive hemagglutination (RPHA) and radioimmunoassay (RIA) procedures. The most sensitive methods for the detection of antibody to HBsAg (anti-HBs) are passive hemagglutination and radioimmunoassay. The application of these newly developed, highly sensitive procedures for the detection of HBsAg and anti-HBs to seroepidemiological studies has resulted in a considerable extension of our knowledge of the natural history of hepatitis type B, and further reduction in the incidence of posttransfusion hepatitis (PTH). However, preliminary data suggest that even the most sensitive test for HBsAg will not detect all units of blood capable of transmitting PTH. The residual, potentially infectious units may possible be identified by applying tests for the detection of antibody to the hepatitis B core antigen, or by developing techniques for the identification of other agenst, including hepatitis type A, which may be implicated in the transmission of hepatitis through blood transfusion.