Analytic and Clinical Utility of a Next-Generation, Highly Sensitive Cardiac Troponin I Assay for Early Detection of Myocardial Injury

Abstract

Improvements in cardiac troponin (cTn) assays have increased the rapidity with which clinicians can identify patients with changing cTn concentrations (rise or fall) indicative of acute myocardial injury. The aim of the present study was to characterize a new, high-sensitivity cTnI (hs-cTnI) assay and examine whether increased sensitivity can result in still earlier detection of evolving injury. We determined the limit of detection, precision profiles, and preliminary estimates of the 99th percentile for the Beckman Coulter hs-cTnI assay in 125 healthy individuals (age <55 years, 54% male). We compared AccuTnI and hs-cTnI to assess whether change criteria for early concentration changes (i.e., > or =3SD for low concentrations and 20% difference for concentrations >0.10 microg/L) were exceeded in the first 2 specimens (median time between specimens, 1 h; 25th-75th percentile, 1-3 h) from subjects with symptoms suggestive of cardiac ischemia (n = 290). The limit of detection for the hs-cTnI assay was 2.06 ng/L, and the 20% CV and 10% CV concentrations were 2.95 and 8.66 ng/L, respectively. The preliminary 99th percentile estimates in lithium heparin, serum, and EDTA plasma were 9.20, 8.00, and 8.60 ng/L, respectively. In 108 patients with myocardial injury based on the peak AccuTnI concentration, applying the change criteria on the 2 earliest specimens identified 81% (95% CI 73%-88%) of patients using the hs-cTnI assay compared to 62% (53%-71%) using the AccuTnI assay (P < 0.001). Although more extensive validation studies are required, this Beckman Coulter hs-cTnI assay appears to detect patients with evolving myocardial injury earlier.