High-sensitivity troponin can rule out MI in many patients within 2 hours of presentation to the emergency department

Reference

Neumann JT, Twerenbold R, Ojeda F, et al. Application of high-sensitivity troponin in suspected myocardial infarction. N Engl J Med 2019;380(26):2529-2540.

Synopsis

The newer high-sensitivity troponin I and T tests are able to detect lower levels of troponin, and therefore may be more accurate at diagnosing myocardial infarction soon after the onset of chest pain. These researchers combined individual patient level data from 15 prospective cohort studies with a total of 23,327 patients who presented to the emergency department (ED) with clinically suspected MI. All of the studies measured troponin I or T on presentation to the ED and serially thereafter; patients with ST elevation were excluded. The authors used data from 9604 patients in 5 cohorts to develop their risk stratification tool, and data from 13,047 patients in the remaining 10 cohorts to validate it. This kind of "geographic validation," in which a clinical prediction rule is developed in a center (or centers) and then is validated in others (rather than just a random split sample) is a more robust and believable validation. The researchers evaluated both short-term outcomes (risk of MI or death within 30 days) and 1- to 2-year outcomes for a subset of patients. The median age of participants was 62 years, 62% were men, and 36% had a history of coronary artery disease. Although all studies obtained troponin at presentation, the interval between that initial sample and resampling varied. The authors grouped patients into early resampling (after 45 minutes to 120 minutes) and late resampling (from 120 minutes to 210 minutes). They then summarized various combinations of the initial troponin level and the resampling level using a unique disk-shaped display tool for identifying patients at low and high risk of MI. For example, a patient with an initial troponin I level of less than 4 ng/L at ED presentation and a second value (1 hour later) that has risen by less than 3 ng/L has a negative predictive value of 99.7% (95% CI 99.4 - 99.8) for MI and a 0.2% 30-day risk of MI or death. The calculator is also available at www.compass-mi.com. The long-term risks for patients who have MI ruled out are also presented. For example, a patient with an initial troponin I level of 2.5 ng/L has a 2% 1-year risk and 3.5% 2-year risk of MI or death, compared to 0.9% and 2.3%, respectively, in a general population sample of patients.