Hepatitis b testing reagent and method

Abstract

A test reagent reagent for HB.sub.s A.sub.g is prepared by applying to a suitable substrate, such as a polystyrene bead, a first coat of purified HB.sub.s A.sub.g to an extent which will permit complete coverage by anti-HB.sub.s. After washing HB.sub.s A.sub.g coated substrate, serum containing anti-HB.sub.s, or an IgG fraction of serum containing anti-HB.sub.s, is applied as a second coat as a second coat in an amount which substantially completely occupies the reacting sites of the HB.sub.s A.sub.g on the outside of the substrate and leaves an excess of antibody reacting groups in a free state, and any unattached material is washed off. A test sample which is to be tested for HB.sub.s A.sub.g is then contacted with the reagent thus produced, permitting attachment of HB.sub.s A.sub.g if present, and washing is done. Then a source of anti-HB.sub.s, such as an IgG fraction containing anti-HB.sub.s, which has been radioactively labeled, is brought into contact with the reagent is brought into contact with the reagent, and any unattached material is washed off. The presence or absence of HB.sub.s A.sub.g in the test sample is determined sample is determined from the presence or absence of significant additional radiation coming from the reagent as compared with a control. This method and its double coated test reagent permits securing high sensitivity without any manufacture of 'dissociated' anti-HB.sub.s separately from the process itself, for use at any stage of the process, which separate manufacture of 'dissociated' anti-HB.sub.s is a difficult and expensive procedure which adds greatly to the expense of any radioimmunoassay which calls for it to be done.