Immunoradiometric assay of serum thyroid stimulating hormone (TSH) as a first-line test in a mixed hospital population.

An immunoradiometric assay of thyroid stimulating hormone (TSH-IRMA) was evaluated as a first-line test for the diagnosis of thyroid disease in a prospective study of 318 consecutive patients in a major city hospital. The results of TSH-IRMA were compared with the diagnoses made by means of our usual diagnostic methods. Based on previous studies a serum TSH level of 0.15 mU/l was chosen as cutoff limit for calculation of diagnostic performance. For patients with serum TSH greater than 5.0 mU/l the results of TSH-IRMA were in accordance with the results of our routine radioimmunoassay. Patients with serum TSH levels between 0.15 mU/l and 5.0 mU/l were euthyroid (the diagnostic sensitivity was 100%). Consequently, the final diagnosis could be made with one test and within two days for 88% of patients. Patients with serum TSH less than 0.15 mU/l needed supplementary tests since only 32% of these patients had thyrotoxicosis, 32% had a non-toxic goiter, and 36% had no thyroid disease.