High-Sensitivity Troponin Assays in Patients With Suspected ACS
- Three different high-sensitivity assays for troponin are FDA approved for clinical use, with differences in analytic sensitivities and reference ranges.
- There is significant disagreement between assays at levels below the limit of detection, and between the limit of detection to the 99th percentile, but not for measures >99th percentile.
- A comprehensive clinical evaluation remains the cornerstone of decision making in patients suspected of acute coronary syndrome, with troponin testing being an adjunct to that assessment.
Do differences in assay characteristics for high-sensitivity cardiac troponin (hs-cTn) impact the management of acute coronary syndrome (ACS)?
The authors measured troponin using three hs-cTn assays (Roche Diagnostics, Elecsys 2010 platform; Abbott Diagnostics, ARCHITECT i2000SR; Siemens Diagnostics, HsVista) in 624 patients with suspected ACS enrolled in the ROMICAT (Rule Out Myocardial Infarction/Ischemia Using Computer Assisted Tomography) I and II trials. ROMICAT included patients with suspected ACS who had a negative conventional troponin measured and who were then subsequently referred for noninvasive testing. The authors assessed the agreement between assays in their classification according to the following groups: < limit of detection (LOD), LOD-99th percentile, and >99th percentile. They also assessed the agreement among assays in classifying the patients as “rule-out,” “observe,” and “rule-in” using the 0/2-hour algorithm developed for each of these assays. In secondary analyses, the authors examined the association of the different assays with diagnostic test findings (coronary angiography, perfusion imaging, and coronary computed tomography angiography).
The average age of patients was 52.8 years of age, and 39.4% were women. A total of 7.9% (n = 49 of 624) had an adjudicated diagnosis of ACS. The proportion of samples with an hs-cTn measurement of
There are significant differences between hs-cTn assays in stratifying individual samples and patients with intermediate likelihood of ACS according to analytical benchmarks that may result in different management recommendations.
Three high-sensitivity assays are Food and Drug Administration (FDA) approved for the measurement of troponin (Elecsys 2010 for hs-cTnT, Roche Diagnostics, Penzberg, Germany; ARCHITECT i2000SR for hs-cTnI, Abbott Diagnostics, Irving, TX; and HsVista for hs-cTnI, Siemens Diagnostics, Newark, DE). Each has specific cut-points used in diagnostic algorithms, which differ due to the differences in sensitivities and reference populations used to derive these cut-points. This study is the first to highlight the discordance between these assays not only in terms of measurement value, but in their overall classification, with consequences impacting decision making. Given the overall excellent diagnostic properties of these three assays, the authors surmise that the discordance is likely related to the characteristics of the populations from which these cut-points are derived. One proposed solution is to use values to express likelihood of ACS in a probabilistic fashion rather than an absolute rule-in and rule-out. Such an approach would be a better complement to a comprehensive clinical evaluation, which remains the cornerstone of the evaluation of patients suspected with ACS; with troponin testing being an adjunct in that assessment.
Clinical Topics: Acute Coronary Syndromes, Invasive Cardiovascular Angiography and Intervention, Noninvasive Imaging, Interventions and ACS, Interventions and Imaging, Angiography, Computed Tomography, Nuclear Imaging
Keywords: Acute Coronary Syndrome, Coronary Angiography, Diagnostic Imaging, Diagnostic Tests, Routine, Limit of Detection, Myocardial Infarction, Myocardial Ischemia, Outpatients, Perfusion Imaging, Troponin I, Troponin T, Tomography, X-Ray Computed
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