The problem of the demonstration of hepatitis B antigen in faeces and bile.

Attempts to detect hepatitis B antigen in faeces and bile should take into account the degradation and disappearance of the surface antigens in an environment containing proteolytic enzymes in the presence of bile salts as in the intestinal lumen. The cores of the Dane particles are much more stable than the surface antigens and these may best be identified by immune electron microscopy using core antibody.