Absolute and Relative Kinetic Changes of High-Sensitivity Cardiac Troponin T in Acute Coronary Syndrome and in Patients with Increased Troponin in the Absence of Acute Coronary Syndrome

BACKGROUND: We evaluated kinetic changes of high-sensitivity cardiac troponin T (hs-cTnT) in patients with acute coronary syndrome (ACS) and patients with hs-cTnT increases not due to ACS to rule in or rule out non-ST-segment elevation myocardial infarction (STEMI). METHODS: hs-cTnT was measured serially in consecutive patients presenting to the emergency department. Patients with ACS who had at least 2 hs-cTnT measurements within 6 h and non-ACS patients with hs-cTnT concentrations above the 99th percentile value (14 ng/L) were enrolled to compare absolute and relative kinetic changes of hs-cTnT. RESULTS: For discrimination of non-STEMI (n = 165) in the entire study population (n = 784), the absolute delta change with the ROC-optimized value of 9.2 ng/L yielded an area under the curve of 0.898 and was superior to all relative delta changes (P < 0.0001). The positive predictive value for the absolute delta change was 48.7%, whereas the negative predictive value was 96.5%. In a specific ACS population with exclusion of STEMI (n = 342), the absolute delta change with the ROC-optimized value of 6.9 ng/L yielded a positive predictive value of 82.8% and a negative predictive value of 93.0%. In comparison to the >= 20% relative delta change, the ROC-optimized absolute delta change demonstrated a significantly added value for the entire study population and for the ACS cohort (net reclassification index 0.331 and 0.499, P < 0.0001). CONCLUSIONS: Absolute delta changes appear superior to relative delta changes in discriminating non-STEMI. A rise or fall of at least 9.2 ng/L in the entire study population and 6.9 ng/L in selected ACS patients seems adequate to rule-out non-STEMI. However, delta-values are useful to rule-in non-STEMI only in a specific ACS population. (C) 2011 American Association for Clinical Chemistry