ABSTRACT
The use of labels and labeled reagents in immunoassays dates back to 1930’s when Reiner suggested to use a label to facilitate monitoring of an immunoreaction (1). Erythrocytes were first described as labels by Stavitsky and Arquilla in 1953 (2) who used them as labels in a homogeneous immunoassay. Radioactive labels emerged during the 1950’s for quantitation of serum antibodies with a method subsequently named the Farr assay (3). The introduction of competitive radioimmunoassay in the late 1950’s by Yallow and Berson (4,5) actually started the development of modem immunoassay technology and since then radioimmunoassays have rapidly gained widespread acceptance, first in the field of endocrinology, and later in other fields of clinical analysis. The first radioimmunoassays were soon followed by non-isotopic assays in the form of enzymatic and fluorescence-based techniques, and today nonradioisotopic assays are rapidly replacing radioactive techniques in clinical immunoassays. That development is more slowly taking place in hybridization assays and receptor-ligand binding assays.
