A new generation of tests enables accident and emergency clinicians to accurately “rule in” or “rule out” a myocardial infarction within one hour of the onset of chest pain, according to researchers.
Results from a study appear to confirm the efficacy of high-sensitive troponin assays for diagnosing heart attack in patients with acute chest pain even more rapidly than previously thought.
“Patients no longer have to wait for three or more hours in the emergency department”
The tests, which can measure small changes in the level of troponin – a heart muscle protein that is released into the blood stream during a heart attack – have become popular in recent years, as they provide quicker results than earlier generations of less sensitive tests for detecting troponin release.
Two of the new high-sensitive assays were recommended for use by the NHS in 2014 by the National Institute for Health and Care Excellence – Roche’s Elecsys troponin T high-sensitive assay and the ARCHITECT STAT high-sensitive troponin-I assay, made by Abbott.
In its guidance, NICE noted that the tests offered a marked improvement on the time needed to carry out standard cardiac troponin tests, delivering results in three to four hours as opposed to 10 to 12.
But the latest trial, which involved a new algorithm for analysing results from Roche’s assay, suggested waiting times could be reduced even further.
It reduced the observation time needed to rule-in or rule-out an MI from three to six hours to just one hour, according to a team of international researchers in the Annals of Emergency Medicine.
The study involved 1,282 patients in 12 hospitals across nine countries, of which 16.6% went on to have a final diagnosis of acute myocardial infarction.
Using the algorithm, 63.4% of patients were classified as “rule-out”, 14.4% were classified as “rule-in”, and 22.2% were classed as “indeterminate” and triaged for observation.
MI diagnosis now possible within one hour using troponin tests
It resulted in a negative predictive value and sensitivity for acute MI of 99.1% in the rule-out group, a positive predictive value and specificity for acute MI of 77.2% and 96.1% in the rule-in group, and a prevalence of acute MI of 22.5% in the observational group.
The researchers concluded that the algorithm “performs well for early rule-out and rule-in of acute myocardial infarction”.
Study author Christian Mueller, professor of cardiology at the University of Basel in Switzerland, said: “Thanks to this new approach, we can now shorten the time to heart attack diagnosis for millions of patients presenting in emergency rooms with acute chest pain all over the world.
“Patients no longer have to wait for three or more hours in the emergency department, not knowing whether they have an acute, life-threatening disease or if their chest pain is caused by other reasons,” he added.
The European Society of Cardiology adopted the concept behind the test at their annual meeting in London in August, with its new clinical guidelines supporting the one-hour diagnostic algorithm with high-sensitive troponin testing.