Three hundred and fifty specimens from a selected group of hospital patients were tested for the presence of hepatitis B antigen (HB-Ag) by radioimmunoassay (RIA), micro-complement fixation test (CFT) and eounter-immunoelectrophoresis (CIEP).I~IA detected 82 (23.7 per cent), CFT 63 (18 per cent), and CIEP only 43 (12.2 per cent) HB-Ag positive sera.All sera found positive by CFT and CIEP were also positive by I~IA. No serum was found positive by CFT or CIEP that was negative by RIA.The problem of anticomplementary activity was solved by absorbing the sera with fluorocarbon instead of guinea pig complement.For our selected group, I~IA was the most sensitive method for the detection of HB-Ag in human sera, followed by CFT and CIEP.
SummaryAn increase in incubation temperature under humid conditions, and a decrease in an incubation time was used to shorten the radioimmunoassay (I~IA) method for hepatitis B antigen (HB-Ag) assay. Incubation of the serum to be tested at 47 ~ C for 120 minutes for primary adsorption was as sensitive as the regular test at room temperature (I~T ~ for 16 hours. In addition, the washing procedure for the removal of labelled antibody was shortened. In order to break hepatitis B antigenantibody (ttB-Ag-Ab) complexes before testing the HB-Ag, sera were heated at 56 ~ C for 30 minutes and then retested by I~IA. The heating of the sera resulted in a 2 per cent higher yield of HB-Ag positives. Therefore, we recommend that sera be heated before testing for HB-Ag.
Introduetiongadioimmunoassay (RIA) is a sensitive method for the detection of hepatitis B antigen (HB-Ag) (MILLER and MORDECAI, 1972 ; GINSBEtm, BASTCaOFT and CONX~AD, 1972). However, the routine application of radioimmunoassay in the laboratory diagnosis of hepatitis B as developed by Abbott Laboratories 1 is limited, because it is relatively expensive and has a lengthy procedure. The current radioimmunoassay method involves at least 16 hours incubation. We, therefore, were interested in shortening this procedure in order to obtain faster results.It is known that, antigen-antibody reactions are temperature-dependent (EAGLE, 1932; ]3OYD, 1956). Therefore, an increase in incubation temperature should result in a decrease in Ag-Ab reaction time and provide a more rapid method. We studied the application of different temperatures and incubation times in the radioimmunoassay procedure.
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