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Objective: Validation of the LT-SYS quantitative in vitro copper assay on a Roche Cobas 8000 c502 analyzer and comparison with a BIOMED assay on a Roche Cobas Mira analyzer. Methods: Imprecision and bias were quantified at different concentration levels (serum and plasma) over a 20-day period. Linearity was assessed covering a range from 4.08 mmol/L to 33.8 mmol/L. Limit of blank (LoB) and limit of detection (LoD) were established based on a total of 120 blank and low-level samples. The method comparison was based on 58 plasma samples. Results: Within-run imprecision ranged from 0.7% to 1.2% and within-laboratory imprecision from 1.4% to 3.3%. Relative bias for the 2 serum pools with known target values was less than 2.5%. The assay did not deviate from linearity over the tested measuring range. LoB and LoD were 0.12 mmol/L and 0.23 mmol/L, respectively. The method comparison revealed an average deviation of 11.5% (2.016 mmol/L), and the linear regression fit was y=1.464 + 0.795x. Conclusions: The LT-SYS copper assay characterized in this study showed a fully acceptable performance with good degrees of imprecision and bias, no deviation from linearity in the relevant measuring rangem, and very low LoB and LoD. [ABSTRACT FROM AUTHOR]