Automated quantification of TSH in serum by a chemiluminescent enzyme immunometric assay: analytical validation

Thyroid stimulating hormone (thyrotropin; TSH) in serum was assayed with the Immulite-TSH, a fully automated solid-phase third-generation immunoassay analyzer that has a chemiluminescent detection system. The intraassay CV ranged from 3.6% to 6.2% for TSH mean concentrations from 0.025 to 32.12 mIU/L and the interassay CV ranged from 7.9% to 10% for TSH mean concentrations between 0.023 and 31.93 mIU/L. The analytical and functional detection limits of the assay were 0.001 and 0.0068 respectively. No interference was observed by any of the compounds: bilirubin, triglycerides, and hemoglobin. To compare the accuracy of Immulite-TSH with that of a conventional immuno-radiometric assay (Orion Diagnostica Irma-TSH), we examined 153 patient samples with TSH concentrations ranging approximately 0.2 to 100 mIU/L. At TSH concentration approximately 0.15 the precision was greater for Immulite-TSH than for Irma TSH (3.8% vs 11.87%) intraassay CV and (8.6% vs 35.4%) interassay CV. We concluded that Immulite-TSH is a rapid and precise third-generation assay, totally automated and the results can be provided to the clinician within 1 to 2 h of receipt of the patient's sample.