title: One-step, labeled-antibody assay for measuring free thyroxin. I. Assay development and validation.
abstract: We describe a one-step, labeled-antibody radioassay for measuring free thyroxin (FT4) in serum or plasma, based on a novel principle. FT4 in the sample competes with a gross molar excess (over antibody) of a cross-reactant (L-triiodothyronine, T3), chemically coupled to magnetizable polymer particles, for binding to avid 125l-labeled monoclonal anti-thyroxin antibodies. As in conventional immunoassays, 125I counts bound to the solid phase (T3-magnetizable particles) are inversely proportional to sample FT4 concentration. We demonstrate here the development and technical validity of this new method.
authors.affiliation: Amerlite Diagnostics Ltd., Cardiff Laboratories, Whitchurch, U.K.
authors.forename: N D
authors.initials: ND
authors.lastname: Christofides
authors.forename: C P
authors.initials: CP
authors.lastname: Sheehan
authors.forename: J E
authors.initials: JE
authors.lastname: Midgley
mesh_terms: D000911:Antibodies, Monoclonal; D000915:Antibody Affinity; D006801:Humans; D007457:Iodine Radioisotopes; D008280:Magnetics; D008863:Microspheres; D011863:Radioimmunoassay / Q000379:methods*; D012709:Serum Albumin / Q000378:metabolism; D013974:Thyroxine / Q000097:blood* / Q000276:immunology; D013975:Thyroxine-Binding Proteins / Q000378:metabolism; D014284:Triiodothyronine / Q000097:blood / Q000276:immunology
chemical_list: D000911:Antibodies, Monoclonal; D007457:Iodine Radioisotopes; D012709:Serum Albumin; D013975:Thyroxine-Binding Proteins; D014284:Triiodothyronine; D013974:Thyroxine