New Approach in Immunometric Assays

Since their development in the 1960s, immunoassays have been used analytically in a wide variety of biological fields (1). Their success is largely due to the remarkable ability of antibodies to recognize molecules with high affinity and specificity in very complex media, such as biological fluids (blood, urine) and cellular or tissular extracts. Since the pioneering work of Yalow and Berson, immunoassays have been developed which exploit different types of analyte (hapten or antigen), tracer, (analyte or specific antibody), antibody specific to the analyte (monoclonal or polyclonal antibodies), labeling (radioactive, enzymatic, fluorescent, luminescent...), and methodology (homogeneous or heterogeneous assays depending on whether or not there is a step to separate the bound and free forms of the analyte). The two broad categories of assays (2), competitive assays and two-site immunometric assays, essentially differ in the nature of the analyte, the concentrations of the components in the immunological reaction, and the nature of the tracer (analyte or specific antibody).