Lowering the troponin I diagnostic threshold improves ACS outcomes
MedWire News: The use of a sensitive troponin I assay in patients admitted to hospital with suspected acute coronary syndrome (ACS) can improve diagnosis and clinical outcomes, study findings suggest.
The researchers, writing in JAMA, say that lowering the diagnostic threshold could help to identify patients at risk for adverse events and better target preventive measures.
A team led by Nicholas Mills (University of Edinburgh, UK) evaluated the diagnostic performance of the latest generation of sensitive troponin assays among consecutive patients admitted with suspected ACS to the Royal Infirmary of Edinburgh.
The study had two phases: a validation phase (n=1038), during which the threshold of detection for myocardial necrosis was 0.20 ng/ml, and an implementation phase (n=1054), when the threshold was reduced to 0.05 ng/ml. The same highly sensitive troponin I assay was used in both phases.
Patients were then followed-up for 1 year for the primary endpoint of recurrent myocardial infarction (MI) or death.
Mills et al stratified patients into three groups according to their troponin I levels on admission. Levels were <0.05 ng/ml in 64% of patients, 0.05-0.19 ng/ml in 8%, and ≥0.20 ng/ml in 28%, and these proportions did not differ markedly between the two study phases.
During the validation phase, the primary endpoint occurred in 7%, 39%, and 24% of patients in the troponin <0.05, 0.05-0.19, and ≥0.20 ng/ml groups, respectively.
During the implementation phase, the primary endpoint occurred in 5%, 21%, and 24% of patients in the troponin <0.05, 0.05-0.19, and ≥0.20 ng/ml groups, respectively.
Thus, for patients with troponin I levels in the 0.05-0.19 ng/ml range, lowering the diagnostic threshold from 0.20 to 0.05 ng/ml was associated with a significantly lower risk for death/recurrent MI at 1 year (odds ratio=0.42).
The better outcome can be attributed to differences in management during admission, say the authors. For example, patients who met the diagnostic criteria were more likely to be referred to a cardiologist, receive dual antiplatelet therapy, undergo coronary revascularization, and receive secondary prevention measures, than those who did not.
"In conclusion, the use of a sensitive troponin assay in patients with suspected ACS increased the rate of diagnosis of MI and identified a high-risk group of patients," Mills et al write. "Lowering the diagnostic threshold for MI was associated with an immediate and substantial improvement in the clinical management and outcome of patients with suspected ACS."
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By Joanna Lyford