Evaluation of a semi-automatic radioimmunoassay for hepatitis B surface antigen (HBsAg).

The recently developed semi-automatic Hepatube system was evaluated in comparison to another radioimmunoassay for the detection of hepatitis B surface antigen (HBsAg), the manual Ausria II-125 test. After incubation of serum in anti-HBs coated tubes, the Hepatube system uses a machine to wash the tubes and to add tracer. After a second incubation, tubes are washed again in the machine and are manually transferred to the gamma counter. Two machines were used. Machine 1 had an undefined defect. Of 1490 samples tested, 69 (4.6%) gave false-positive results versus 11 (0.7%) in the Ausria II-125 test. Machine 2 had one false-positive result among 920 samples versus 5 in the Ausria II-125 test. The sensitivity was measured with reference panels from Wellcome and Abbott as well as in titration series. The Hepatube system was found to be a factor three less sensitive than the Ausria II-125 test. The Hepatube processor is easy to handle; radioactive material can be held at a distance during the whole procedure; waste material is limited and less voluminous than in the Ausria II-125 test.