CHEMILUMINESCENT 3RD-GENERATION ASSAY (AMERLITE TSH-30) OF THYROID-STIMULATING HORMONE IN SERUM OR PLASMA ASSESSED

We assessed the laboratory performance and clinical utility of a new c ommercial third-generation assay of thyroid-stimulating hormone (TSH), Amerlite TSH-30. The interassay CV was 6% at TSH concentrations of ap proximately 0.08 mIU/L, and the analytical and functional detection li mits of the assay were 0.005 and 0.0125 mIU/L, respectively. Although the assay recovered approximately 96% of TSH International Reference P reparation (TSH-IRP) 80/558 added to serum samples, the endogenous TSH concentrations in basal samples were significantly lower than those f ound by using two other TSH assays; bias data obtained from thyroliber in stimulation tests suggested that the negative bias found with TSH-3 0 may be due to the heterogeneity of TSH in basal samples. TSH-30 comp letely discriminated hyperthyroid and hypothyroid patients from euthyr oid ambulatory patients but also detected TSH (>0.0125 mIU/L) in 3 of 46 untreated hyperthyroid patients. Compared with two second-generatio n assays, TSH-30 better discriminated between patients with subnormal TSH due to hyperthyroidism, thyroxine overreplacement, and nonthyroida l illness but there was still significant overlap between results for these groups.