Sera and questionnaires were evaluated retrospectively from 128 volunteer blood donors whose blood had been implicated in cases of clinically recognized post-transfusion hepatitis in recipients of one- or two-unit blood transfusion between 1971 and 1977. Serologic markers of hepatitis B virus (HBV) infection were found in 23 percent, compared to 9.7 percent of 3,230 prospective blood donors. The prevalence of antibody to hepatitis A virus was similar among implicated donors (44%), prospective donors (58%), and among those implicated donors with (41%) and without (44%) HBV markers. Among implicated donors, none had a history at the time of donation of having had clinically recognizable hepatitis, 93 percent had no history of prior blood transfusion, and 80 percent had normal hepatic enzymes. Data from this study confirm that non-A, non-B hepatitis has been a common form of posttransfusion hepatitis in recent years, since 77 percent of these implicated donors had no HBV serologic markers. In addition, these donors could not be distinguished by age, race, sex, history of clinical hepatitis or of prior blood transfusion, or in most cases by hepatic enzyme levels.

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The results of hepatitis B surface antigen (HBs-Ag) testing in a large volunteer blood donor population are described. Counterelectrophoresis and three versions of solid-phase radioimmunoassay technic are compared and evaluated. Initial results suggested that the radioimmunoassay technic are compared and evaluated. Initial results suggested that the radioimmunoassay technic detected more than five times as many reactive donors as did counterelectrophoresis. The specificity of the radioimmunoassay technic has been increased by successive modifications, and recent results show that the technic detects 73 percent more reactive donors than does counterelectrophoresis. Not all of these reactions are specific, and it is estimated that the true gain in detection of HBsAg carriers is 49 percent of the value found by counterelectroesis. The incidence of HBsAg carriers in the America Red Cross donor population is about 1.25 per 1,000.

Blood collected by 11 Red Cross Regional Blood Centers were screened by the method of agar gel diffusion (AGD) for the presence of hepatitis-B antibody. Of the 185,134 units tested, 114 were found to be positive for HBAb by the Regional Centers and were forwarded to National Special Projects Laboratory for confirmation. Only five out of 114 samples revealed lines of identity with a control anti-HBAg when reacted with a pool of plasma positive for hepatitis-B antigen that was different from that which was provided to the Centers. Apparently, the precipitation reactions observed by the Centers were largely due to the antithrombin antibodies in the donors' sera reacting with the residual thrombin used by the manufacturer to convert HBAg positive plasma to serum. We conclude that the incidence of hepatitis-B antibody as measured by agar gel diffusion in the Red Cross Blood donor population was extremely low.