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Incremental Value of High-Sensitivity Cardiac Troponin T for Risk Prediction in Patients With Suspected Acute Myocardial Infarction
Study Questions:
Can a high-sensitivity assay further improve risk stratification compared with a standard cardiac troponin assay in chest pain patients?
Methods:
A total of 1,159 consecutive patients presenting with acute chest pain were included, 30% of whom were diagnosed with acute coronary syndrome. Blood samples were drawn at the time of presentation. Cardiac troponin T (cTnT) was measured with a standard fourth-generation assay and a high-sensitivity assay (hs-cTnT) (both Roche Diagnostics). Follow-up was 24 months.
Results:
Death occurred in 76 patients, and 42 had an acute myocardial infarction (AMI). Prognostic accuracy of hs-cTnT for death was significantly higher (area under receiver operating characteristic curve [AUC], 0.79; 95% confidence interval [CI], 0.74-0.84) than that of cTnT (AUC, 0.69; 95% CI, 0.62-0.76; p < 0.001). After adjustment for Thrombolysis in Myocardial Infarction (TIMI) risk score (that included the cTnT assay result), hs-cTnT above the 99th percentile (0.014 µg/L) was associated with a hazard ratio for death of 2.60 (95% CI, 1.42-4.74). Addition of hs-cTnT to the risk score improved the reclassification of patients (net reclassification improvement, 0.91; 95% CI, 0.67-1.14; p < 0.001). Subgroup analyses showed that this effect resulted from the better classification of patients without AMI at time of testing. Hs-cTnT outperformed cTnT in the prediction of AMI during follow-up (p = 0.02), but was not independently predictive for this endpoint.
Conclusions:
Concentrations of hs-cTnT >0.014 µg/L improve the prediction of death, but not subsequent AMI, in unselected patients presenting with acute chest pain.
Perspective:
This is a potentially important paper on the use of the hs-cTnT assay. Elevations above the 99th% upper reference limit were predictive of long-term mortality (24 months), but not recurrent AMI after adjustment for other risk factors. Despite that, it was more predictive than the previous standard fourth-generation assay. A key issue is that elevations associated with AMI may provide a different prognostic profile than those with elevations of hs-cTnT, which are common with these high-sensitivity assays whenever structural heart disease is present. Structural heart disease is likely to be prognostic in the longer-term, whereas elevations associated with AMI are likely to play out in the shorter-term. This analysis fails to evaluate this potentially important distinction.
Keywords: Acute Coronary Syndrome, Myocardial Infarction, Follow-Up Studies, Area Under Curve, Risk Factors, Prognosis, Biomarkers, Chest Pain, Cardiovascular Diseases, ROC Curve, Confidence Intervals, Troponin
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