Comparative determination of total serum thyroxine. Radio-immunoassay and protein-binding assay

The precision, accuracy, sensitivity and clinical results of a radio-immunological method for the determination of total serum thyroxine are compared with similar criteria of a competitive protein-binding assay. Application of both methods in the assay of thyroxine in 150 serum samples gave good agreement between the two techniques. The radio-immunoassay offers certain methodological advantages and is considerably less costly than thyroxine determinations in which commercially available kits are used.