Analytical performance of the fully automated AxSYM (R) estradiol assay

The test performance of the fully automated AxSYM(R) Estradiol available on the immunoassay analyser Abbott AxSYM(R) was evaluated. Imprecision, sensi tivity and linearity of dilution were examined. For assessment of accuracy, the assay results measured in 12 control pools and 9 patient samples were compared with the values obtained with isotope dilution - mass spectrometry (reference method). The correlation with the manual radioimmunoassay Estra diol MAlA(R) was evaluated using 140 serum samples with estradiol concentra tions ranging from 0 to 10 nmol/l. Imprecision studies revealed for the AxS YM(R) Estradiol within-run coefficients of variation of 2.8-8.4% and day-to -day coefficients of variation of 3.4-9.5% (concentration range 0.3-2.8 nmo l/l). The lower limit of quantification (lowest estradiol concentration wit h a day-to-day coefficient of variation <20%) was <0.11 nmol/l; the lower l imit of detection was <0.05 nmol/l. The estradiol concentration recovered i n patient samples after dilution did not differ by more than 10% from the e xpected values. The estradiol concentration measured with the AxSYM(R) Estr adiol in 12 commercial control pools in some cases grossly deviated from th e reference method values; however, for 9 individual patient samples the Ax SYM results deviated by not more than 22% (-11% - +22%). There was a good o verall correlation (coefficient of correlation = 0.989) between the results measured with the AxSYM(R) Estradiol and the Estradiol MAlA(R) in patient samples. The AxSYM(R) Estradiol assay exhibits a good precision and a sufficient deg ree of sensitivity for measurement of estradiol in serum of menstruating wo men. Although the AxSYM results measured in the control pools, in some case s did not meet the target values, the good correlation with the Estradiol M AlA(R) indicates that the reliability of the AxSYM(R) Estradiol for clinica l practice is comparable with well established radioimmunoassays. Thus, the AxSYM(R) Estradiol offers an alternative which is comparable with respect to clinical reliability but has great advantages in view of rapidity, flexi bility and convenience of analysis.