Functional sensitivity of seven automated thyroid stimulating hormone immunoassays

Background: Serum thyroid stimulating hormone (TSH) measurements are useful for detecting clinical and subclinical primary hypo- and hyperthyroidism in ambulatory patients. For diagnosis of hyperthyroidism, the functional sensitivity (FS) is an important performance criterion, and current guidelines recommend an FS of <= 0.02 m IU/1 for "third" generation performance. Methods: We evaluated TSH FS for the Access 2, Advia Centaur, Architect i2000. Dimension ExL Modular Analytics E170, Immulite 2000 and Dimension Vista 1500 automated immunoassays using serum pools tested over a 6 week period using 2 reagent lots and 2 calibrations. FS was determined by fitting a power function to the imprecision data using KaleidaGraph software. Results: The FS (m IU/1) for Access 2, ADVIA Centaur, ARCHITECT i2000, Dimension ExL, Modular Analytics E170, Immulite 2000, and Dimension Vista 1500 systems were determined to be 0.039, 0.006, 0.007, 0.003, 0.008, 0.003, and 0.003, respectively. The lowest and next to lowest pools had overall mean TSH concentrations of 0.012 m IU/1 and 0.020 m IU/I, respectively and a range of concentrations of 0.005 to 0.022 m IU/1 and 0.007 to 0.077 m IU/I, respectively. Conclusions: All assays showed excellent performance in FS consistent with a "third" generation claim except for the Access 2 system. Further harmonization of TSH immunoassays is required, especially at lower concentrations. (C) 2011 Elsevier B.V. All rights reserved.