High-sensitivity cardiac troponin I at presentation in patients with suspected acute coronary syndrome: a cohort study

Abstract

Background: Suspected acute coronary syndrome is the commonest reason for emergency admission to hospital and is a large burden on health-care resources. Strategies to identify low-risk patients suitable for immediate discharge would have major benefits.

Methods: We did a prospective cohort study of 6304 consecutively enrolled patients with suspected acute coronary syndrome presenting to four secondary and tertiary care hospitals in Scotland. We measured plasma troponin concentrations at presentation using a high-sensitivity cardiac troponin I assay. In derivation and validation cohorts, we evaluated the negative predictive value of a range of troponin concentrations for the primary outcome of index myocardial infarction, or subsequent myocardial infarction or cardiac death at 30 days. This trial is registered with ClinicalTrials.gov (number NCT01852123).

Findings: 782 (16%) of 4870 patients in the derivation cohort had index myocardial infarction, with a further 32 (1%) re-presenting with myocardial infarction and 75 (2%) cardiac deaths at 30 days. In patients without myocardial infarction at presentation, troponin concentrations were less than 5 ng/L in 2311 (61%) of 3799 patients, with a negative predictive value of 99·6% (95% 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 less than 5 ng/L in 594 (56%) of 1061 patients, with an overall negative predictive value of 99·4% (98·8-99·9). At 1 year, these patients had a lower risk of myocardial infarction and cardiac death than did those with a troponin concentration of 5 ng/L or more (0·6% vs 3·3%; adjusted hazard ratio 0·41, 95% CI 0·21-0·80; p<0·0001).

Interpretation: Low plasma troponin concentrations identify two-thirds of patients at very low risk of cardiac events who could be discharged from hospital. Implementation of this approach could substantially reduce hospital admissions and have major benefits for both patients and health-care providers.

Funding: British Heart Foundation and Chief Scientist Office (Scotland).

Figure 1

Cardiac troponin I concentration at presentation and risk of myocardial infarction (A) Negative predictive value of a range of troponin I concentrations at presentation for the composite outcome of index myocardial infarction, and myocardial infarction or cardiac death at 30 days. (B) Cumulative proportion of patients with suspected acute coronary syndrome with troponin concentrations below each threshold.

Figure 2

Negative predictive value of troponin concentrations <5 ng/L at presentation, stratified by subgroups For the composite outcome of index myocardial infarction, and myocardial infarction or cardiac death at 30 days. Dashed line is the prespecified negative predictive value of 99·5%.

Figure 3

Cumulative incidence of myocardial infarction or cardiac death in patients with troponin concentrations less than the 99th centile Patients without index myocardial infarction were stratified into two groups based on the troponin concentration at presentation. Compared to patients with troponin concentrations ≥5 ng/L, patients with troponin concentrations <5 ng/L were less likely to have a myocardial infarction or cardiac death at 1 year (0·6% vs 3·3%; hazard ratio 0·41, 95% CI 0·21–0·80; log-rank p<0·0001).