Pre-evaluation and system optimization of the Elecsys thyroid electrochemiluminescence immunoassays

We present the results of a pre-evaluation of the thyroid function test free thyroxine, free triiodothyronine and third generation TSH using the Elecsys electrochemiluminescence immunoassay system. A collaborative field study between the development center of the manufacturer and a clinical chemistry laboratory addressed the reliability and comparability of the new Elecsys assays to established methods under clinical laboratory conditions using samples from routine in vitro thyroid testing. Preliminary (reference) formulations of the reagents and several electrochemiluminescent pilot models were used for assay measurements, either in the company's research center or in the clinical setting. The new thyroid assays were compared with the respective Enzymun-Test assays, performed on the ES300 automated immunoassay analyzer. A WHO standard was used for standardization of TSH, whereas an equilibrium dialysis method was applied for free triiodothyronine. The free thyroxine assay was standardized against the Enzymun-Test free thyroxine assay, which had previously been calibrated against equilibrium dialysis. The aim of this field study was to support the optimization of the technology used for Elecsys in an early stage of development and thereby prepare the ground for the adaptation of the immunoassays to the final Elecsys 2010 random access analyzer. A subsequent multicenter evaluation demonstrated that the requirements of routine thyroid testing in terms of reliability were fulfilled by the system.