Economy and efficiency in routine thyroid-function testing: use of a sensitive immunoradiometric assay for thyrotropin in a general hospital laboratory.
We measured thyrotropin (TSH) with a sensitive immunoradiometric assay (IRMA) in 2329 consecutive serum samples received for thyroid-function tests from hospital and general practice. Of these, 185 (7.9%) had TSH values less than 0.2 milli-int. unit/L: 33 (1.4%) were hyperthyroid, 20 (0.9%) were being treated for hyperthyroidism, 115 (4.9%) were receiving L-thyroxin, and 17 (0.7%) were clinically euthyroid but had severe non-thyroidal illnesses. In the first 506 serum samples, we also measured free thyroxin, free triiodothyronine (FT3), and total thyroxin. Thyroliberin (thyrotropin-releasing hormone, TRH) tests performed on 84 patients showed that an undetectable initial TSH (usually ascribable to therapy with thyroxin) predicted a flat TRH response. All untreated thyrotoxic patients had undetectable TSH. Experience confirmed that this TSH assay, in conjunction with a supplementary assay of FT3 when the TSH concentration is less than twice the limit of detection, is efficient and economical for routine evaluation of thyroid function in an unselected population.
D000328:Adult; D000368:Aged; D002624:Chemistry, Clinical / Q000191:economics*; D006769:Hospitals, General; D006801:Humans; D008875:Middle Aged; D010865:Pilot Projects; D011446:Prospective Studies; D013960:Thyroid Function Tests / Q000191:economics*; D013963:Thyroid Hormones / Q000097:blood; D006113:United Kingdom
D013963:Thyroid Hormones