Can Troponin Assays Rule Out Myocardial Infarction Within an Hour?

High-sensitivity troponin I levels that remain normal 1 hour after presentation can accurately rule out acute myocardial infarction (AMI), according to 2 new studies.

Early diagnosis of AMI in patients presenting with acute chest pain improves clinical outcomes. However, there is currently no quick and accurate method of diagnosing AMI. Therefore, researchers investigated whether testing cardiac troponin levels can enhance the accuracy and speed of diagnosis.

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o investigate this theory, the researchers in the first study tested a 1-hour algorithm to diagnose AMI using a high-sensitivity troponin I assay with a cutoff level of 6 ng/L. 1

The researchers examined 1040 patients in the Biomarkers in Acute Cardiac Care study who presented to the emergency department with acute chest pain from July 19, 2013, to December 31, 2014. The results were validated against 2 independent cohorts of 4009 patients.

After analyzing the data, the researchers found that the 1-hour approach was comparable with a 3-hour approach. The negative predictive value was 99.8%, and sensitivity was 99.1%.

“Patients with possible AMI can be triaged within 1 hour after admission with no loss of safety compared with a 3-hour approach, when a low and sensitive cutoff is applied,” the researchers concluded. “This concept enables safe discharge or rapid treatment initiation after 1 hour.”

In the second study, the researchers determined the diagnostic performance of low concentrations of high-sensitivity cardiac troponin I in patients with suspected cardiac chest pain and an electrocardiogram showing no ischemia as an indicator of AMI. 2

The researchers pooled data from 5 international, prospective, observational cohort studies that included 3155 patients with symptoms of cardiac ischemia. The patients underwent an electrocardiogram and high-sensitivity troponin test at presentation between November 1, 2007, and August 10, 2013.

Test results showed that 9.2% of patients had had an AMI. A limit of 1.2 ng/L had a negative predictive value of 99.5% and sensitivity of 99.0%.

“High-sensitivity troponin I concentrations determined at presentation to the ED that were below the limit of detection identified 18.8% of patients potentially suitable for discharge, with a high sensitivity for acute myocardial infarction,” the researchers concluded. “Rounded cutoff values above the limit of detection may not have the required sensitivity for clinical implementation.”

—Amanda Balbi

References:

  1. Neumann JT, Sörensen NA, Schwemer T, et al. Diagnosis of myocardial infarction using a high-sensitivity troponin I 1-hour algorithm [published online June 1, 2016]. JAMA Cardiol. doi:10.1001/jamacardio.2016.0695.
  2. Carlton E, Greenslade J, Cullen L, et al. Evaluation of high-sensitivity cardiac troponin I levels in patients with suspected acute coronary syndrome [published online June 1, 2016]. JAMA Cardiol. doi:10.1001/jamacardio.2016.1309.