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Troponin threshold identifies patients at low risk for MI in ED

Researchers have identified a cardiac troponin threshold that can potentially detect two-thirds of patients presenting in ED at very low risk for myocardial infarction or cardiac death, and may be able to be safely discharged, according to recently published data in The Lancet.             

“Over the last two decades the number of hospital admissions due to chest pain has tripled. The overwhelming majority of these patients do not have a heart attack. This study shows that low plasma cardiac troponin concentrations at presentation identify up to two-thirds of patients who are at very low risk of heart attack and could be safely discharged from the ED. Use of this approach is likely to have major benefits for both patients and health care providers,” Anoop S V Shah, MD, a clinical research fellow at the University of Edinburgh, Scotland, said in a press release. 

To determine the level of plasma troponin that would identify patients with suspected acute coronary syndrome who have a low risk of myocardial infarction (MI) and may be suitable for immediate discharge, Shah and colleagues conducted a prospective study of 6,304 patients presenting to the ED with chest pain.

A high-sensitivity cardiac troponin I assay, which is more sensitive than the standard version and can detect far lower levels of troponin in the blood, was used to measurer plasma troponin concentrations, according to a press release. 

Results demonstrated that of the 4,870 patients in the study’s derivation group, 16% had index MI and 1% had re-presented with MI.

Troponin concentrations were less than 5 ng/L in 2,311 patients without MI, for a negative predictive value of 99.6% (95% CI, 99.3–99.8) for the primary outcome, according to the researchers. 

No difference in negative predictive value was seen in groups stratified by age, sex, risk factors and previous cardiovascular disease.

Among patients in the validation cohorts, 56% of patients had troponin concentration of less than 5 ng/L, with a negative predictive value of 99.4% (95% CI, 98.9–99.9). 

Compared with patients who had troponin concentrations of 5 ng/L or more, patients with troponin concentrations of less than 5 ng/L had a lower risk of MI and cardiac death at 1 year after discharge, according to the researchers.

Shah and colleagues noted that their findings will potentially prevent the need for repeat testing and the incorporation of clinical risk scores for accelerated diagnoses, as well as reduce the number of potentially unnecessary hospital admissions. 

“Until now there were no quick ways to rule out a heart attack within the ED. We have identified a cardiac troponin concentration (less than 5 ng/L) below which patients are at very low risk of heart attack either during the admission or in the ensuing 30 days. These patients are therefore potentially suitable for immediate and safe discharge from the ED. These findings could dramatically reduce unnecessary hospital admissions and provide substantial cost savings for health care providers,” Shah said in the release. – by Casey Hower

Disclosures: Shah reports being a consultant for Abbott Laboratories. Please see the full study for a list of all authors’ relevant financial disclosures.