Serial Changes in Highly Sensitive Troponin I Assay and Early Diagnosis of Myocardial Infarction
What is the diagnostic performance of a highly sensitive troponin I (hs-TnI) assay compared with a contemporary troponin I (cTnI) assay and their serial changes in the diagnosis of acute myocardial infarction (AMI)?
A total of 1,818 patients with suspected acute coronary syndrome were consecutively enrolled at the chest pain units of the University Heart Center Hamburg, the University Medical Center Mainz, and the Federal Armed Forces Hospital Koblenz, all in Germany, from 2007 to 2008. Twelve biomarkers including hs-TnI (level of detection, 3.4 pg/ml) and cTnI (level of detection, 10 pg/ml) were measured on admission and after 3 and 6 hours. The main outcome measures were diagnostic performance for AMI of baseline and serial changes in hs-TnI and cTnI results at 3 hours after admission to the emergency department.
Of the 1,818 patients, 413 (22.7%) were diagnosed as having AMI. For discrimination of AMI, the area under the receiver operating characteristic (ROC) curve was 0.96 (95% confidence interval [CI], 0.95-0.97) for hs-TnI on admission and 0.92 (95% CI, 0.90-0.94) for cTnI on admission. Both were superior to the other evaluated diagnostic biomarkers. The use of hs-TnI at admission (with the diagnostic cutoff value at the 99th percentile of 30 pg/ml) had a sensitivity of 82.3% and a negative predictive value (for ruling out AMI) of 94.7%. The use of cTnI (with the diagnostic cutoff value at the 99th percentile of 32 pg/ml) at admission had a sensitivity of 79.4% and a negative predictive value of 94.0%. Using levels obtained at 3 hours after admission, the sensitivity was 98.2% and the negative predictive value was 99.4% for both hs-TnI and cTnI assays. Combining the 99th percentile cutoff at admission with the serial change in troponin concentration within 3 hours, the positive predictive value (for ruling in AMI) for hs-TnI increased from 75.1% at admission to 95.8% after 3 hours, and for cTnI increased from 80.9% at admission to 96.1% after 3 hours.
The authors concluded that among patients with suspected acute coronary syndrome, hs-TnI or cTnI determination 3 hours after admission may facilitate early rule-out of AMI.
In the current study, application of a next-generation hs-TnI assay provided excellent diagnostic discrimination for both the rule-out and rule-in of MI even in patients presenting within the first hours after chest pain onset. Rule-in of MI with ensuing adequate treatment initiation was facilitated by the utilization of serial hs-TnI changes. Furthermore, the relative change in concentration of hs-TnI within 3 hours after admission in addition to the 99th percentile diagnostic cutoff provides a substantially improved positive predictive value for the diagnosis of MI when compared with hs-TnI determination on admission alone. Based on available data, it appears that application of the relative change in hs-TnI or cTnI concentration within 3 hours after admission, in combination with the 99th percentile diagnostic cutoff value on admission, improves specificity and may facilitate an accurate early rule-in of MI.
Keywords: Outcome Assessment (Health Care), Myocardial Infarction, Acute Coronary Syndrome, Biological Markers, Chest Pain, Troponin I, Cardiology, Sensitivity and Specificity, Cardiovascular Diseases, Germany
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