High-Sensitivity Troponin I and Acute Coronary Syndrome
What is the threshold of a high-sensitivity cardiac troponin I assay that identifies patients with suspected acute coronary syndrome at low risk of myocardial infarction (MI) and potentially suitable for immediate discharge?
The High-STEACS trial investigators conducted a prospective cohort study of 6,304 consecutively enrolled patients with suspected acute coronary syndrome presenting to four secondary and tertiary care hospitals in Scotland. They measured plasma troponin concentrations at presentation using a high-sensitivity cardiac troponin I assay. In derivation and validation cohorts, they evaluated the negative predictive value of a range of troponin concentrations for the primary outcome of index MI, or subsequent MI or cardiac death at 30 days.
Out of 4,870 patients in the derivation cohort, 782 (16%) had index MI, with a further 32 (1%) re-presenting with MI and 75 (2%) cardiac deaths at 30 days. In patients without MI at presentation, troponin concentrations were <5 ng/L in 2,311 (61%) of 3,799 patients, with a negative predictive value of 99.6% (95% confidence interval [CI], 99.3-99.8) for the primary outcome. The negative predictive value was consistent across groups stratified by age, sex, risk factors, and previous cardiovascular disease. In two independent validation cohorts, troponin concentrations were <5 ng/L in 594 (56%) of 1,061 patients, with an overall negative predictive value of 99.4% (95% CI, 98.8-99.9). At 1 year, these patients had a lower risk of MI and cardiac death than did those with a troponin concentration of ≥5 ng/L (0.6% vs. 3.3%; adjusted hazard ratio, 0.41; 95% CI, 0.21-0.80; p < 0.0001).
The authors concluded that low plasma troponin concentrations identify two-thirds of patients at very low risk of cardiac events who could be discharged from the hospital.
This study reports that use of a high-sensitivity cardiac troponin threshold <5 ng/L at presentation identifies almost two-thirds of patients as being at very low risk of MI or cardiac death, and who could potentially be safely discharged from the emergency department. Implementation of this approach would reduce avoidable hospital admission and have major benefits for both patients and health care providers. Additional studies are indicated to validate these findings and assess the clinical and cost-effectiveness of this approach in routine clinical practice.
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