Objective: To investigate whether a high-sensitivity troponin assay, shown to improve early detection of acute myocardial infarction (AMI), permits accelerated rule-in/rule-out of AMI.
Methods: Patients who presented to the emergency department within 4 h of the onset of chest pain suggestive of acute coronary syndrome were prospectively recruited from November 2007 to April 2010. Blood samples were taken at 0, 1, 2 and 12-24 h after presentation and were analysed for clinically applied troponin I and for high-sensitivity troponin T (hsTnT). The dynamic change in hsTnT levels between time points was measured. The primary outcome was admission diagnosis of AMI.
Results: Of the 385 patients recruited, 82 (21.3%) had AMI. The sensitivity of hsTnT by 2 h was 95.1% (88.7-98.1%), specificity 75.6% (73.8-76.5%), positive predictive value 53.8% (50.2-55.5%) and negative predictive value 98.3% (96.0-99.3%). The sensitivity was not statistically different between peak values at 2 h and 24 h. Adding ECG results reduced the false negative rate to 1.2%. The additional application of ≥20% delta criterion over the 2 h period for 0-2 h samples increased specificity to 92.4% (90.2-94.3%) but reduced sensitivity to 56.1% (48.0-63.2%).
Conclusion: hsTnT taken at 0 and 2 h after presentation, together with ECG results, could identify patients suitable for early stress testing with a false negative rate for AMI of 1.2%. Further trials of such an approach are warranted. The specificity of hsTnT for diagnosing AMI could be improved by the use of a delta of ≥20%, but at the cost of major reductions in sensitivity.