The use of several markers of hepatitis B infection to monitor risks of infection in a haemodialysis unit and in laboratories.

INTRODUCTION The test for HBsAg, anti-HBsAg, anti-HBcAg and DNA polymerase activity may be used not only as markers for hepatitis B infection but they may also be used as indicators for the stage of the infective process. HBsAg is first detected in the serum during the incubation period over 6 26 weeks (1~ 6~ months) or less and during the early phase (first 2 3 weeks) of the acute infection (Hoofnagle, 1979). In many cases of acute infection HBsAg may only be detected in the serum for a few days. In SOI1le patients, HBsAg may persist despite clinical improvement indicating that a chronic form of hepatitis or a chronic carrier state may be developing (Hoofnagle, 1979). Anti-Hfs., is usually detected during the mid to late period of convalescence form of infection. Usually there is a variable interval between the disappearance of HBsAg and the appearance of anti-HBs' In general the presence of antibody is presumptive evidence of a previous infection and immunity to hepatitis B virus (Hoofnagle, 1979). Anti-Hfs., is