Stratus® CS cardiac troponin I method: performance characteristics including imprecision at low concentrations

Objectives: Define performance characteristics of the Stratus® CS cardiac troponin I (cTnI) assay in routine practice. Methods: Imprecision at low cTnI values was assessed according to NCCLS EP5-A. Linearity was assessed by regression analysis; the reference interval was determined in 345 healthy individuals. Minimum detectable concentration (MDC) was assessed with 20 replicates of zero calibrator, and method correlation and bias (n = 77) were by Passing–Bablok regression and Bland–Altman plot. Results: cTnI of 0.06 μg/l corresponded to the 10% CV; the 99th percentile of the reference population was 0.07 μg/l. Linearity extended from 0 to 50.0 μg/l and the MDC was 0.010 μg/l. The method comparison equation was Stratus® CS = 1.00 (Dimension® RxL)–0.02 μg/l with no bias. Conclusions: The Stratus® CS cTnI assay in routine practice has performance characteristics appropriate for clinical use, including good correlation to a central laboratory cTnI method and imprecision of a high sensitivity troponin method with a CV of <10% at the 99th percentile of the reference population.