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One-step, labeled-antibody assay for measuring free thyroxin. I. Assay development and validation
N D Christofides1, C P Sheehan, J E Midgley
1Amerlite Diagnostics Ltd., Cardiff Laboratories, Whitchurch, U.K.
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.
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.
