A solid-phase radioimmunoassay of serum dehydroepiandrosterone sulphate using a monoclonal antibody

A monoclonal antibody directed against dehydroepiandrosterone, but with high affinity for dehydroepiandrosterone sulphate (DHA-S), has been used to develop a solid phase radioimmunoassay for measuring serum DHA-S. The antibody was covalently linked to polyacrylamide microbeads with no change in binding characteristics. The procedure requires only the chromatography of serum on anion-exchange cellulose before assaying the equivalent of 0.25 microliter serum. The method is precise, accurate and specific and can detect 19.5 pg of DHA-S. Serum DHA-S levels measured by this method were in good agreement with those found in a validated radioimmunoassay method involving hydrolysis. The method is quick and one operator could assay 50 blood specimens per day. DHA-S levels in serum from 50 men and 86 women were in agreement with those in the literature. With the availability of theoretically limitless quantities of consistently high quality monoclonal antibodies the advantages of developing solid phase radioimmunoassays for steroids is discussed.