Analytical and clinical evaluation of an automated high-sensitivity cardiac troponin I assay for whole blood.

Objectives: To evaluate the performance of the iStar high-sensitivity cardiac troponin I (hs-cTnI) assay, focusing on its sensitivity, precision, linearity, and consistency with plasma samples, and to establish sex-specific 99th percentile upper reference limits.

Methods: The iStar hs-cTnI assay was assessed using the Drawray iStar 500 analyzer. Key performance metrics such as the limits of blank (LoB), detection (LoD) and quantitation (LoQ), precision, linearity, and agreement between sample types were evaluated according to Clinical and Laboratory Standards Institute (CLSI) guidelines. A methodological comparison was performed with the Abbott ARCHITECT hs-cTnI assay, and cross-reactivity with others troponins was assessed.

Results: The iStar hs-cTnI assay demonstrated robust sensitivity with a LoB of 0.09 ng/L and LoD of 0.31 ng/L. The LoQ was 0.79 ng/L for 20 % coefficient of variation (CV) and 1.85 ng/L for 10 % CV. Precision testing revealed CVs of 1.4-4.8 % near the 99th percentile upper reference limit (URL). The assay exhibited excellent linearity (r=1.00) and high agreement between whole blood and plasma samples (slope=0.936). Methodological comparison with the Abbott ARCHITECT hs-cTnI showed a high correlation coefficient of 0.983. Cross-reactivity with skeletal muscle troponin I, cardiac troponin C, and cardiac troponin T was negligible. In healthy individuals, the overall 99th percentile URL was 16 ng/L, with sex-specific values of 18 ng/L for males and 14 ng/L for females.

Conclusions: The iStar hs-cTnI assay demonstrates high sensitivity and precision, supporting it suitable for the rapid diagnosis of acute myocardial infarction using whole blood samples. Its high agreement with plasma and established sex-specific URL support its potential for clinical use in acute coronary syndrome management.