Immunometric Assay

Immunometric assays are immunoassays in which the tracer is a labeled binder. Most immunometric assays involve two binders, both present in excess. The first binder is usually absorbed onto a solid phase and is used to capture the ligand (analyte). The second binder, the tracer, binds to another epitope on the ligand analyte. Both binders are present in large excess. These assays are sometimes called sandwich binding assays. Presumably, all of the analyte is bound in these binder-ligand-binder complexes. As the concentration of analyte is increased, the measured response is increased. The standard curve of an immunometric assay has a positive slope and is often asymmetrical.