Henry Ford Hospital Medical Journal


New immunoradiometric assays (IRMAs) that detect low concentrations of thyroid-stimulating hormone (TSH) have recently become available for routine diagnostic use. These new assays have the putative advantage over conventional radioimmunoassay in that they can distinguish hyperthyroidism from euthyroidism by the finding of a serum TSH below the normal limit. In the present study we sought to evaluate four of these kits according to analytical performance characteristics and clinical utility. All IRM As could detect TSH at a concentration substantially below the lower limit of normal and thus effectively identify hyperthyroid samples. Although differences in the performance characteristics were found, all assays were clearly superior to the conventional radioimmunoassay. It is recommended that IRMAs for TSH be used as routine diagnostic tests for thyroid dysfunction. Their full value in the assessment of hyperthyroidism and other thyroid disorders has yet to be determined.