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Biomarkers for Predicting Serious Cardiac Outcomes at 72 Hours in Patients Presenting Early After Chest Pain Onset With Symptoms of Acute Coronary Syndromes
Study Questions:
What is the comparative value of nine different markers for predicting short-term complications in low-risk patients admitted for possible acute coronary syndrome?
Methods:
The authors used the initial serum sample of 186 patients presenting to the emergency department within 6 hours of chest pain onset, and measured: creatine kinase (CK), CK-MB, enhanced AccuTnI (Beckman Coulter), high-sensitivity troponin T (hs-TnT), ischemia-modified albumin, interleukin-6 hs-cTnI (Beckman Coulter; investigation use only), N-terminal pro–B-type natriuretic peptide (NT-proBNP), and cTnI (Abbott AxSym). Patients were followed for 72 hours after presentation and determined whether they experienced the following serious cardiac events: myocardial infarction, heart failure, serious arrhythmia, refractory ischemic cardiac pain, or death. Receiver operating characteristic (ROC) curves were analyzed to determine the area under the ROC curve (AUC) and optimal cutoffs for the biomarkers.
Results:
The AUCs for the hs-cTnI assay (0.86; 95% confidence interval [CI], 0.76-0.96), the AccuTnI assay (0.86; 95% CI, 0.78-0.95), and the hs-cTnT assay (0.82; 95% CI, 0.71-0.94) were significantly higher than those for the other six assays (AUC values ≤0.71 for the rest of the biomarkers, p < 0.05). The ROC curve-derived optimal cutoffs were ≥19 ng/L (sensitivity, 80%; specificity, 88%) for hs-cTnI, ≥0.018 μg/L (sensitivity, 75%; specificity, 86%) for AccuTnI, and ≥32 ng/L (sensitivity, 68%; specificity, 92%) for hs-cTnT.
Conclusions:
The authors concluded that the optimal cutoffs for predicting serious cardiac outcomes in this low-risk population are different from the published 99th percentiles. Larger studies will be required to verify these findings.
Perspective:
This is a potentially important paper and one of the few that compare the ability of several contemporary cTn assays with two hs assays and other biomarkers in an attempt to predict short-term risk in patients presenting within 6 hours of the onset of chest discomfort. The hs assays were superior to the others in predicting events at 72 hours, but at values >99% of the upper reference limit. This may be reality, but in many hospitals, those with elevations in cTn would have had interventions that are not described. In addition, the small sample size (186) means that there are wide confidence limits around the values they report.
Keywords: Coronary Artery Disease, Acute Coronary Syndrome, Myocardial Infarction, Interleukin-6, Creatine Kinase, MB Form, Troponin T, Emergency Service, Hospital, Serum Albumin, Biomarkers, Chest Pain, Troponin I, Heart Failure, Confidence Intervals, Hospitalization, Natriuretic Peptide, Brain
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