High-sensitivity troponin rules out ACS in the ED with 99% accuracy

A blood test for high-sensitivity troponin T (hsTnT) used in emergency departments successfully ruled out myocardial infarction (MI) and helped identify patients at low 30-day risk for adverse cardiac events, researchers reported in JAMA Cardiology.

The test—a fifth-generation Roche Elecsys hsTnT assay—was approved by the FDA in January 2017. Lead researcher W. Frank Peacock, MD, with Baylor College of Medicine, and colleagues studied its use in 15 emergency departments (EDs) across the U.S. from 2011 to 2015 when the company was working with the FDA to evaluate the assay.

In a study of 1,600 patients presenting to EDs with suspected acute coronary syndrome (ACS), Peacock and co-authors found an hsTnT value less than 6 nanograms per liter had a negative predictive value of 99.4 percent for acute MI. In 974 patients who were tested both upon presentation to the ED and three hours later, serial hsTnT levels below 19 ng/L were associated with a 99.3 percent negative predictive value for adverse cardiac events within 30 days—defined as MI, urgent revascularization or death. The test was similarly effective in men and women.

The authors noted more than seven million patients present to EDs each year in the United States with symptoms that could be attributed to ACS, but approximately 90 percent won’t have a heart attack.

“Identifying a low-risk cohort may permit early ED discharge and avoid unnecessary hospitalization,” Peacock and colleagues wrote. “Rapid turnaround of low-risk patients could translate into a reduction in ED volumes, which would benefit patients (shorter waiting times, increased satisfaction, improved outcomes, and saved costs), clinicians (decreased diagnostic ambiguity and medicolegal burden) and hospitals (by providing cost-saving benefits).”

They also pointed out the hsTnT assay’s ability to rule out more than 99 percent of 30-day adverse events meets “an acceptable ACS risk-stratification strategy for discharge.”

“This 1 percent rate represents the breakpoint between the risk of unnecessary hospitalization resulting in morbidity from a hospital-acquired condition and the potential harm from an inappropriate ED discharge,” Peacock et al. wrote.

The 19 ng/L cutoff—the 99th percentile in the U.S.—differs from the 14 ng/L threshold used globally, but the researchers said clinicians should consider geographically specific cardiovascular risk factors into their reference levels.

In an accompanying editorial, Frederick K. Korley, MD, PhD, points out the study reported 44 percent of patients with suspected ACS are low risk and can potentially be discharged after two hsTnT measurements. That represents a marked contrast from the 20 to 30 percent of patients with suspected ACS who have been defined as low risk in studies of current-generation troponin assays.

“If the findings of Peacock et al. hold true on further validation, implementation of hsTn tests could be the game changer we have been waiting for,” he wrote. “It will provide clinicians with objective data to support early discharge of patients who are low risk.”

However, Korley suggested caution when implementing hsTnT tests into routine practice. He pointed out the three-hour troponin sample was more predictive than the first test, making it likely the prognostic value of the initial test hinges on how quickly a patient presents to the ED.

Korley added it is unrealistic to expect one biomarker to perfectly separate MI patients from non-MI patients. However, “it is likely that if other aspects of the clinical evaluation … are taken into consideration, the small proportion of MIs that are missed by the 0-hour and three-hour hsTnT results may be correctly diagnosed nonetheless,” he wrote.