Absolute Change in High-Sensitivity Cardiac Troponin I at Three Hours After Presentation is Useful for Diagnosing Acute Myocardial Infarction in the Emergency Department

Background: A rise and/or fall in cardiac troponin value with at least one value above the 99th percentile upper reference limit is essential for acute myocardial infarction (AMI) diagnosis. We evaluated the clinical usefulness of serial high-sensitivity cardiac troponin I (hs-cTnI) measurements in AMI diagnosis, in terms of the predictability of absolute and relative changes. Methods: For this retrospective, forward observational study, we enrolled 281 patients older than 18 years who presented with chest pain at the emergency department (ED) between August 2015 and December 2016. The patients were grouped as AMI and non-AMI, and 73 (26%) were diagnosed as having AMI. Hs-cTnI (Abbott Diagnostics, Abbott Park, IL, USA) was measured at presentation and 3 hours later. We assessed the diagnostic performance of the absolute and relative changes in hs-cTnI. Results: The cut-off values to predict AMI were 16.2 ng/L and 42.1% for the absolute and relative hs-cTnI changes, respectively. The area under the curve of hs-cTnI for AMI diagnosis was larger for absolute changes than for relative changes [0.96 (95% confidence interval [CI], 0.92-0.98) vs 0.89 (95% CI, 0.85-0.93)] (P=0.014). Conclusions: The absolute hs-cTnI change at 3 hours after presentation was superior to the relative change, and a rise and/or fall in hs-cTnI of >16.2 ng/L at 3 hours after presentation was useful to identify AMI in patients presenting at the ED.