Immunoassay utilizing biotin bridge with universal solid phase

An immunoassay utilizing a biotin bridge is performed with a solid phase with anti-biotin immobilized on its surface. In accordance with the assay, the solid phase is incubated with a biotinylated binding species, preferably biotinylated antibody, specific for the ligand to be detected. This is then reacted with the test sample, followed by a labeled binding member, either in a sandwich-type or competitive-type binding assay. The label is then detected in accordance with conventional detection techniques. Use of the solid phase with only a biotin-specific antibody attached thereto expands the utility and versatility of a single solid phase for use in the detection of an unlimited variety of ligands.