Development and Preliminary Clinical Validation of a High Sensitivity Assay for Cardiac Troponin Using a Capillary Flow (Single Molecule) Fluorescence Detector

Abstract

The European Society of Cardiology and the American College of Cardiology (ESC/ACC) have redefined the criteria for the diagnosis of acute myocardial infarction, requiring an increase in the concentration of cardiac troponin in the clinical context of myocardial ischemia (1). A subgroup of this committee has recommended that the cutoff concentration be established at the 99th percentile of the reference range, with an acceptable interassay imprecision of ≤10% (2). The use of a low troponin cutoff concentration enables the detection of more patients who have minor myocardial damage and are at short-term risk for adverse cardiac events (3). In a study conducted by the IFCC, none of the manufacturers of troponin assays cleared by the Food and Drug Administration in 2004 had a sensitivity for detecting troponin at the 99th percentile with the requisite precision (4). Therefore, troponin assays with higher analytical sensitivity and precision are needed to meet the guidelines of The European Society of Cardiology and the American College of Cardiology. We examined the analytical performance of the ZeptX™ System (Singulex) assay for cardiac troponin I (cTnI), evaluating its sensitivity, precision, and recovery. We assessed the assay’s clinical performance by comparing assay results for 97 specimens from patients with chest pain with results from the 1st-generation Bayer Centaur cTnI assay. With samples from 88 healthy individuals, we determined the 99th percentile cutoff for the ZeptX assay. We also determined the analytical limit of detection (LoD) across 15 sequential assays and calculated the LoD as the mean value of the zero standard plus 3 SDs from quadruplicate intraassay determinations. The ZeptX System consists of flow …