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

Abstract

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.

Figures

Figure 1:

Recruitment of patients presenting with chest pain, and results of early measurement of high-sensitivity troponin T levels according to recommended cut-off point of 99th percentile of the general population (14 ng/L). MI = non–ST-segment elevation myocardial infarction.

Figure 2:

Receiver operating characteristics curve for the high-sensitivity troponin T assay at two hours after presentation for the diagnosis of non–ST-segment elevation myocardial infarction. Area under the curve = 0.93 (95% confidence interval 0.91–0.95).

Figure 3:

Sensitivity of the high-sensitivity troponin T assay at presentation at different cut-off points for the diagnosis of non–ST-segment elevation myocardial infarction (MI), by time from symptom onset. Cutoff points: 14 ng/L = 99th percentile of the general population; 5 ng/L = limit of detection (the lowest quantity or concentration of an analyte that can be reliably detected with a given analytical method); 3 ng/L = limit of blank (the highest apparent concentration of an analyte expected to be found in a sample containing no analyte).

Figure 4:

Kaplan–Meier survival curves for adverse outcomes (death, nonfatal myocardial infarction and heart failure) by one year after presentation according to results of conventional troponin I and high-sensitivity troponin T assays.

Figure 5:

Receiver operating characteristics curves for the high-sensitivity troponin T assay and the conventional troponin I assay for predicting adverse events (death, nonfatal myocardial infarction or heart failure) by one year after presentation. AUC = area under the curve, CI = confidence interval.