High-sensitivity troponin I assays ID patients at lowest, highest risk for acute MI
High-sensitivity cardiac troponin I (hs-cTnI) assays, when considered in the context of appropriate thresholds, can identify and expedite triage of patients at varying levels of risk for myocardial infarction, researchers reported in the Journal of the American College of Cardiology this week.
Corresponding author Fred S. Apple, PhD, of Hennepin County Medical Center in Minneapolis, and colleagues undertook a prospective, observational study of patients with suspected acute MI in an effort to determine whether single-measurement hs-cTnI could identify those at the lowest and highest risks for MI. They evaluated 2,212 patients across 29 sites in the U.S., all of which measured hs-cTnI using Siemens Healthineers’ Atellica IM TnIH or ADVIA Centaur TNIH assays.
Apple and his team said in JACC single-measurement strategies “promise a simple, practical approach” to risk estimation, but while cardiac troponin measurements are used to detect myocardial injury and MI in the U.S., the country has limited clinical experience with high-sensitivity assays. Existing data are either based on the Abbott hs-cTnI assay, which isn’t yet FDA-cleared, or the Roche hs-CTnT assay, which has been federally cleared but only reports down to a limit of quantification of 6 ng/l.
“The improved analytical performance offered by high-sensitivity assays has allowed for the quantification of cardiac troponin at lower concentrations and enabled the development and validation of several novel, rapid risk-stratification strategies that were not possible using contemporary assays,” the authors wrote.
Siemens, based in Erlangen, Germany, received FDA clearance for its hs-cTnI assays in early 2018, offering American physicians another viable tool for risk prediction. It was those tests Apple et al. considered in their work, evaluating positive predictive values and specificities to identify high-risk patients and studying negative predictive values (NPVs) and sensitivities to identify low-risk patients.
Across the study period, acute MI occurred in 12% of patients. The troponin test’s limits of detection (LoD) or quantification (LoQ) resulted in what Apple and co-authors called “excellent sensitivities” ranging from 98.6% to 99.6% and NPVs ranging from 99.5% to 99.8% for acute MI or death at 30 days.
An optimized threshold of less than 5 ng/l identified nearly half of all low-risk patients, resulting in sensitivities of 98.6% and NPVs of 99.6% for acute MI or death at 30 days across both assays. A hs-cTnI result of greater than 120 ng/l identified a subset of high-risk patients, with positive predictive values for acute MI exceeding 70%.
“The superior analytical performance offered by high-sensitivity cardiac troponin assays enables the potential of using a single cardiac troponin measurement at presentation to safely rule out acute MI if the initial results are below analytical thresholds such as the LoD or LoQ concentrations thresholds tailored to maximize efficiency while maintaining safety across both assays,” Apple and colleagues wrote. “In the present study, we identified a concentration threshold of less than 5 ng/l as the optimized concentration that maximized efficiency while maintaining safety across both assays.”
The authors said further randomized studies are necessary to validate their results and confirm the efficiency and safety of risk stratification tools based on single high-sensitivity cardiac troponin measurements.
After graduating from Indiana University-Bloomington with a bachelor’s in journalism, Anicka joined TriMed’s Chicago team in 2017 covering cardiology. Close to her heart is long-form journalism, Pilot G-2 pens, dark chocolate and her dog Harper Lee.