Comparison of Cardiac Troponin I Measurements on Whole Blood and Plasma on the Stratus CS Analyzer and Comparison with AxSYM

Abstract

Assays for cardiac troponin T and troponin I (cTnI) are powerful tools for early identification of patients with acute myocardial infarction (AMI) and for pointing out subjects at highest risk among patients with unstable angina pectoris (1)(2)(3). These applications require increasingly rapid and more sensitive tests. To this end, one of the most commonly used automated assays for cTnI (Stratus® II; Dade) has undergone extensive revision (4)(5). A second-generation quantitative radial partition immunoassay is now used in combination with the Stratus CS fluorometric analyzer, a system designed to meet the needs of STAT and point-of-care testing. The Stratus CS yields cTnI results that are clinically consistent with those obtained with the Stratus II (6). The Stratus CS uses closed routine sample tubes containing anticoagulated whole blood (lithium heparin). The system takes ≤14 min to centrifuge the tube and perform the analysis. The Stratus CS can also manage precentrifuged plasma samples. In the present study, the Stratus CS was used to determine cTnI on whole blood and on preprocessed plasma samples drawn from the same patients. Our purpose was to check the similarity of the results obtained for both samples in the entire measuring range. We also aimed at comparing results from the Stratus CS with cTnI results yielded by the Abbott AxSYM analyzer, with special attention to concentrations below the threshold for AMI. The Stratus CS is a fluorometric enzyme immunoassay analyzer for quantitative determination of the cardiac markers creatine kinase-MB mass, myoglobin, and cTnI (Dade Behring). The test system uses radial partition immunoassay technology, which has been enhanced through the use of a monoclonal capture antibody coupled to Starburst® dendrimers (7). According to the insert for the cTnI method, coronary risk increases at cTnI concentrations >0.4 μg/L, and this value …