Diagnostic and prognostic utility of early measurement with high-sensitivity troponin T assay in patients presenting with chest pain

Background:

High-sensitivity troponin assays are now available for clinical use. We investigated whether early measurement with such an assay is superior to a conventional assay in the evaluation of acute coronary syndromes.

Methods:

Patients presenting to an emergency department with chest pain who did not have ST-segment elevation were prospectively recruited from November 2007 to December 2010. Patients underwent serial testing with a conventional cardiac troponin I assay. Samples were also obtained at presentation and two hours later for measurement of troponin T levels using a high-sensitivity assay. The primary outcome was diagnosis of myocardial infarction on admission; secondary outcomes were death, myocardial infarction and heart failure at one year.

Results:

Of the 939 patients enrolled in the study, 205 (21.8%) had myocardial infarction. By two hours after presentation, the high-sensitivity troponin T assay at the cut-off point of the 99th percentile of the general population (14 ng/L) had a sensitivity of 92.2% (95% confidence interval CI] 88.1%–95.0%) and a specificity of 79.7% (95% CI 78.6%–80.5%) for the diagnosis of non–ST-segment myocardial infarction. The sensitivity of the assay at presentation was 100% among patients who presented four to six hours after symptom onset. By one year, the high-sensitivity troponin T assay was found to be superior than the conventional assay in predicting death (hazard ratio HR] 5.4, 95% CI 2.7–10.7) and heart failure (HR 27.8, 95% CI 6.6–116.4), whereas the conventional assay was superior in predicting nonfatal myocardial infarction (HR 4.0, 95% CI 2.4–6.7).

Interpretation:

The high-sensitivity troponin T assay at the cut-off point of the 99th percentile was highly sensitive for the diagnosis of myocardial infarction by two hours after presentation and had prognostic utility beyond that of the conventional assay. To rule out myocardial infarction, the optimal time to test a second sample using the high-sensitivity troponin T level may be four to six hours after symptom onset, but this finding needs verification in future studies before it can become routine practice.For novel cardiac markers to be clinically useful in diagnosing acute coronary syndromes, they need to show their incremental utility beyond that of existing markers, with therapeutic implications designed to improve patient care. Recent improvement in the performance of troponin assays to comply with current guidelines for the diagnosis of acute myocardial infarction¹ has resulted in a new generation of assays with enhanced clinical sensitivity that are now available for use in clinical care. Assays with high sensitivity have been shown to detect myocardial injury earlier^2–8 and identify more patients at risk of future adverse outcomes^8–10 than conventional assays.We conducted a study to assess whether early measurement (at presentation and two hours later) with a high-sensitivity troponin T assay could (a) effectively rule out myocardial infarction without the need for later measurement of troponin levels and (b) identify more patients at risk of adverse cardiac events within one year follow-up compared with a conventional troponin assay.