Among the several methods employed for the detection of
hepatitis B antigen (
HBAg) and
hepatitis B antibody (HBAb), radioimmunoassay is considered to be the most sensitive and specific. This paper describes a radioimmunoprecipitation test (RIP) for
HBAg and HBAb standardized in our laboratory; it consists of a double-antibody precipitation test in a micro-titer system employing 125I-labeled
HBAg. The test is compared with double immunodiffusion (ID) and with counterimmunoelectrophoresis (CEP) in the detection of
HBAg and HBAb in healthy persons and in patients with acute and chronic
liver disease. RIP is 20,000 times more sensitive than ID and 2,500 times than CEP when
HBAg is tested, and 40,000 times more sensitive than ID and 10,000 times than CEP for the antibody detection. Moreover the method is reproducible and specific for
HBAg and HBAb. With this test the frequency of
HBAg in healthy persons was 0% in subjects without any known contact with antigenic material, 0.80% in hospital personnel and 1.17% in high risk personnel (laboratory technicians, blood products workers, ecc.). In acute viral
hepatitis the frequency of
HBAg was 90% at the admittance to the hospital and 70% at the dimission, while CEP detected a frequency of 85% and 20% respectively. In chronic
liver disease the frequency of
HBAg with the RIP method was 83.3% in
chronic persistent hepatitis, 42.8% in chronic aggressive
hepatitis, 23% in
cryptogenic cirrhosis and 16.6% in
alcoholic cirrhosis. The frequency of HBAb detected with RIP was 4.50% in subjects without any known contact with antigenic material, 6.45% in hospital personnel, 0.41% in high risk personnel, 20% in acute viral
hepatitis at the admittance to the hospital and 50% at the discharge, 25% in
chronic persistent hepatitis, 14.2% in chronic aggressive
hepatitis, 15.3% in
cryptogenic cirrhosis and 50% in
alcoholic cirrhosis. The high frequency of antibody in healthy persons with no history of
hepatitis or parenteral exposure to
blood transfusion suggests a widespread diffusion of
hepatitis B infection and the possibility of a nonparenteral route transmission. The frequency of
HBAg and HBAb in chronic
liver disease as detected by a very sensitive method rises the question of a possible role of hepatitis B virus in the pathogenesis of the disease.