Radioimmunoassays and 2-Site Immunoradiometric “Sandwich” Assays: Basic Principles

Abstract

The“sandwich”or noncompetitive reagent-excess, 2-site immunoradiometric assay (2-site IRMA), ELISA, USERIA, and related techniques, have several advantages compared with the traditional or competetive radioimmunoassays. IRMAs can provide improved sensitivity and specificity. However, IRMAs present some practical problems with nonspecific binding, increased consumption of antibody, biphasic dose response curve, (high dose hook effect), and may require special technieues for dose response curve analysis. We anticipate considerable growth in the popularity and importance of 2-site IRMA.