title: Homogeneous time-resolved fluoroimmunoassay of thyroxin in serum.
abstract: We describe a rapid, simple nonseparation fluoroimmunoassay for determination of thyroxin in serum. The assay is based on the labeling of thyroxin directly with a fluorescent europium chelate, the fluorescence of which is quenched on binding to an antithyroxin antibody. With the assay buffer we used, maximum quenching is 90%. The rapid achievement of equilibrium in the assay solution, regardless of the sequence of reagent additions, allows fast measurement of thyroxin. Precision was good (CV less than 5%) within the clinical range for total thyroxin (50-300 nmol/L), and results correlated well with those by a commercial radioimmunoassay.
mesh_terms: D000911:Antibodies, Monoclonal; D005063:Europium; D005455:Fluorescent Antibody Technique; D006801:Humans; D011863:Radioimmunoassay; D013974:Thyroxine / Q000097:blood*; D013997:Time Factors
chemical_list: D000911:Antibodies, Monoclonal; D005063:Europium; D013974:Thyroxine