[Fluorescent immunoassay of thyroxine in blood serum]

A method of solid-phase fluoroimmunoassay of thyroxine (T4) on polystyrene 96-microtiter plates using coproporphyrin III-labeled antibodies was developed; 0.02 ml of blood serum without preliminary treatment was required. Thimerosal was added to lessen the T4-binding effect of the serum on the results of T4-binding effect of the serum on the results of the immunoassay. A calibration curve was obtained to determine T4 covering the entire physiological range of concentrations (from 3 to 21 micrograms of thyroxine in 100 ml of the serum). A variation coefficient within this range did not exceed 15%. For 14 unknown blood serum samples of patients the coefficient of correlation with the results obtained using a commercial kit for T4 determination (Abbott, USA) was 0.960. The time of the assay was 2-2.5 h. This method is simple and easy for use on a large scale.