Journal ArticleMeasurement of estradiol is useful in assisted reproduction, evaluation of infertility, menopause, and male feminization. The analytic performance of 8 estradiol immunoassays was evaluated. The imprecision and accuracy of the Access, ADVIA Centaur, ARCHITECT i2000, AutoDELFIA, Elecsys 2010, IMMULITE 2000, and Vitros ECi estradiol assays (see text for proprietary information) were evaluated by using an isotope dilution-gas chromatography-mass spectrometry (ID-GC-MS) reference method. The coefficient of variation (CV) ranged from 6.9% on the Elecsys 2010 to 42.6% on the ADVIA Centaur at an estradiol concentration of 18 pg/mL (66 pmol/L), with the ARCHITECT i2000 assay in development and the Vitros ECi having a CV below 10% at this estradiol concentration. Agreement between the automated assays and ID-GC-MS was variable, with slopes ranging from 0.87 to 1.20. The Access, ARCHITECT i2000 in development, and the IMMULITE 2000 were the most accurate, with slopes of 0.99, 0.98, and 1.03, respectively. These findings indicate that the ARCHITECT i2000 estradiol assay in development had the best precision and accuracy of the assays evaluated for measurement of serum estradiol concentrations
