Analytical evaluation of an improved procedure for measuring thyrotropin

The analytical characteristics of the AxSYM Ultrasensitive hTSH-II (Abbott Laboratories) procedure for quantitation of serum thyrotropin (TSH) concentration were evaluated. Within-and between-run imprecisions, functional sensitivity, analytical interval and relative inaccuracy with respect to the Enzymum-Test TSH (Boehringer Mannheim) were studied. In all cases, the within-run and between-run of coefficients variation were lower than 6.69% and 8.12% respectively. The measurement range was tested with serial dilutions of a serum with a high thyrotropin concentration, and the procedure was found to be linear up to at least 87.0 mIU/l. The functional sensitivity was 0.018 mIU/l. The relative inaccuracy study (Passing-Bablok non-parametric linear regression) produced the following linear equation: (AxSYM) = 1.02. (ES-700) - 0.03 mIU/l, with 95% confidence intervals of a (-0.05; -0.01); b (0.98; 1.06).