Received on March 7, 2008
Accepted on October 8, 2008

Proteomics and Protein Markers

Clinical Performance of Two Highly Sensitive Cardiac Troponin I Assays

¹ Department of Medical Sciences, Clinical Chemistry, University of Uppsala, Uppsala, Sweden
² Department of Medical Sciences, Cardiology, and Uppsala Clinical Research Centre, University of Uppsala, Uppsala, Sweden
³ Department of Clinical Chemistry, County Hospital of Gävle, Gävle, Sweden

^* To whom correspondence should be addressed. E-mail: per.venge{at}akademiska.se.

BACKGROUND: The aim of this study was to compare the clinical performance of 2 sensitive cTnI assays with 10% CV imprecision below the 99th percentile upper reference limit.

METHODS: We measured cardiac troponin and N-terminal pro–brain natriuretic peptide (NT-proBNP) concentrations in a random sample of the Global Use of Strategies To Open Occluded Coronary Arteries (GUSTO) IV cohort (n = 1251). Outcome data of 1-year mortality and the composite endpoint DMI [death and/or myocardial infarction (MI) within 30 days] were available in all patients. The 99th percentile of a healthy population was estimated from the Sweden Women and Men and Ischemic Heart Disease (SWISCH) cohort (n = 442). We measured cardiac troponin I (cTnI) using the Access AccuTnI (Beckman Coulter) and Centaur TnI Ultra (Siemens Healthcare Diagnostics) and NT-proBNP using the Elecsys 2010 (Roche Diagnostics).

RESULTS: Applying the 10% CV cutoff, the sensitivity of the Access AccuTnI assay in identifying DMI and death was higher than that of the Centaur TnI Ultra (P = 0.02 and P < 0.001), and the AccuTnI assay also identified more patients at risk (P < 0.001) and with poor outcome. Applying the 99th percentile cutoffs, AccuTnI identified more patients at risk than the Centaur TnI (P < 0.001) and with significant differences in outcome. Significantly more patients with cardiac troponins below the cutoffs as measured by Centaur TnI had increased NT-proBNP concentrations (P < 0.001) compared with AccuTnI.

CONCLUSIONS: The AccuTnI assay identified more patients at risk than the Centaur cTnI Ultra assay. Our results demonstrate the clinical potential of high-sensitivity cardiac troponin assays for the identification of patients at risk of dying from cardiovascular disease.