title: A prospective critical evaluation of in vitro thyroid function tests.
abstract: A number of 2 325 serum samples from a population of in- and outpatients were collected during a six-month period in order to evaluate the usefulness of various thyroid function tests in the clinical laboratory routine. The samples were analysed with the following thyroid function tests: total triiodothyronine (T3) (TT3), total thyroxine (T4) (TT4), free T3 index (FT3I), free T4 index (FT4I) and thyrotropin (TSH). One to two years after the primary evaluation, a follow-up was performed and the final diagnoses were checked in the patients' records. The values of these parameters in the diagnosis of hyperthyroidism were: FT3I greater than FT4I greater than TT3 greater than TT4. The corresponding results in the diagnosis of hypothyroidism were: TSH greater than FT4I greater than FT3I = TT3. No single test could detect both hyper- and hypothyroidism effectively. The only one-step strategy for thyroid evaluation in patients without apparent clinical signs of hyper- or hypothyroidism would therefore be the combined determination of T3 and TSH. The study also showed distinct differences between the reference values of the healthy population and patients without thyroid disorders.
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D002648:Child; D005069:Evaluation Studies as Topic; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D006980:Hyperthyroidism / Q000175:diagnosis; D007037:Hypothyroidism / Q000175:diagnosis; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D013960:Thyroid Function Tests / Q000379:methods*