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.
- high sensitivity troponin
- acute myocardial infarction
- acute coronary syndrome
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Additional materials are published online only. To view these files please visit the journal online (http://dx.doi.org/10.1136/emermed-2011-200222).
Disclosure The TnI assay is that used in the core laboratory for clinical practice. The hsTnT assay was donated by the manufacturer (Roche) who was not responsible for the concept or design of the study and had no role in data analysis, writing up or decision to submit the manuscript.
Funding SA was supported by a National Heart Foundation of New Zealand Research Fellowship. CP holds a Health Research Council of New Zealand Sir Charles Hercus Research Fellowship. This work was supported by the National Heart Foundation and the Health Research Council of New Zealand.
Competing interests None.
Ethics approval Ethics approval was provided by Upper South B regional ethics committee of the Ministry of Health of New Zealand.
Provenance and peer review Not commissioned; externally peer reviewed.