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Undetectable high-sensitivity troponin on presentation rules out AMI

Reuters Health • The Doctor's Channel Daily Newscast

NEW YORK (Reuters Health) – If patients presenting with chest pain have undetectable levels of troponin when tested using a high-sensitivity assay, they almost certainly do not have acute MI, according to findings reported in the September 20 issue of the Journal of American College of Cardiology.

“This research breaks new ground concerning the ability to use novel, high-sensitivity techniques to facilitate the early exclusion of AMI,” the authors comment.

Dr. Richard Body, at the University of Manchester, UK, and colleagues point out that the majority of patients with chest pain are admitted for investigation but relatively few are ultimately diagnosed with AMI. Hence, the ability to exclude AMI early would reduce unnecessary admissions substantially.

In this regard, the team investigated whether the Elecsys high-sensitivity cardiac troponin T (hs-cTnT) assay (Roche Diagnostics), which has a lower detection limit of 3 ng/L, could safely rule out AMI at presentation.

The researchers first tested the idea in a prospective cohort study of 703 patients seeking treatment for chest pain in the emergency department at Manchester Royal Infirmary. Blood was drawn within a median of 3.5 hours of symptom onset for standard and high-sensitivity troponin testing.

Based on standard serial troponin testing, 130 of these patients had an adjudicated diagnosis of AMI. None of the patients who had an hs-cTnT value <3 ng/L at the time of presentation had an AMI, giving a sensitivity of 100.0% and a negative predictive value 100.0%, according to the report.

The high-sensitivity assay could have ruled out AMI a median of 9.6 hours earlier, saving a total of 1547 inpatient hours, the authors calculated.

The investigators then validated the findings in a prospective clinical study involving 915 patients. Only one of the patients with an initially undetectable hs-cTnT had a subsequent rise in troponin. Thus, the sensitivity of an undetectable initial hs-cTnT in ruling out AMI was 99.8%, with a negative predictive value of 99.4%.

This strategy could obviate prolonged evaluation in 4 million of the 15 million patients seen every year for chest pain in emergency departments, Dr. Body and colleagues estimate.

However, they point out, “The novel high-sensitivity troponin assays are yet to be approved for clinical use in the United States, although the hs-cTnT assay reported here has been approved and implemented in parts of Europe.”

They add, “There also have been reports of many other highly sensitive assays. If this approach is applicable to all such novel assays, it would have a profound impact on the ability to evaluate patients rapidly in the ED.”

Reference:
Rapid Exclusion of Acute Myocardial Infarction in Patients With Undetectable Troponin Using a High-Sensitivity Assay
J Am Coll Cardiol 2011;58:1332-1339.