A simple technique for enhancing the sensitivity of a commercial solid-phase radioimmunoassay for hepatitis B surface...

A simple procedural modification of a commercial solid-phase radioimmunoassay technique resulted in increased sensitivity for detecting HBsAg. The main feature of the modification consisted of agitation of the sample and solid-phase antibody during the first incubation. This was achieved by dispensing the bead and sample into a vial and rotating the vial gently during the incubation period. The modified technique resulted in the detection of HBsAg in the range of 1.0 to 1.2 ng/ml (ay subtype) and 0.16 to 0.38 ng/ml (ad subtype). Samples that were reactive by the rotation technique could be shown to be specific by using an immunological neutralization test. Plasma as well as serum could be tested by the rotation technique and gave comparable results when samples were incubated at 45 C or at room temperature. Three (1.3%) of 227 donor samples containing anti-HBc as the sole hepatitis B marker were specifically reactive for HBsAg by the modified procedure, although no sample was reactive by the standard technique.