Detection of Australia antigen by radioimmunoassay.

A double-antibody radioimmunoassay has been developed for the detection of Australia antigen and antibodies to Australia antigen in human sera. The assay is simple to perform, and can be completed in 18 hr. Based on parallel studies of human sera, it is approximately 2000 times more sensitive than agar gel diffusion and 200 times more sensitive than quantitative complement fixation. Australia antigen or antibody to Australia antigen was demonstrated in 22 of 23 single serum samples obtained from patients acutely ill with the long-incubation form of hepatitis; eight of the sera were negative when evaluated by less sensitive techniques.