The detection of hepatitis B surface antigen by radioimmunoassay.

A comparative study was performed to assess the sensitivity and specificity of counterimmunoelectrophoresis (CIEP) and radioimmunoassay (RIA) for the detection of hepatitis B surface antigen. The 8,823 sera examined included selected reference panels and sera collected from populations with low, moderate and high rates of chronic antigen carriage. Overall, hepatitis B surface antigen was detected in 265 sera by CIEP and in 376 by RIA. As well as detecting 46.4% additional positives, the RIA test detected all CIEP-positive sera; i.e., there were no false negative results. However, 150 sera (1.8% of the total tested) gave a positive result by RIA which was not repeatable on retesting. The explanation for this phenomenon appeared to lie in inadequate washing of the antibody-coated tubes.