Ultra-sensitive troponin I levels to exclude acute myocardial infarction from myocardial injury

BACKGROUND: Third generation troponin assays should aid in the rule-out of acute myocardial infarction (AMI). The study aim was to assess the capability of admission measurement of ultra-sensitive troponin I (TnI-Ultra) to exclude AMI from other myocardial injury. METHODS: The first TnI-Ultra sample from 856 patients at presentation to the Emergency Department and subsequent admission to the Cardiac Care Unit were considered in this case series. Myoglobin was simultaneously detected in 684 patients. RESULTS: The sensitivity of the first single TnI-Ultra level was 82.5% in overall AMI, and similar in ST-elevation myocardial infarction (STEMI) and non-ST-elevation myocardial infarction (NSTEMI), admitted, respectively at 3 and 8 h from symptoms. The diagnostic capability of a first single TnI-Ultra level was poor for both STEMI and NSTEMI to discriminate and rule-out overall AMI from myocardial injury, with an area under the receiver-operating curve of 0.65 and a negative likelihood ratio of 0.55. Adopting an optimal test threshold or adding myoglobin detection did not improve TnI-Ultra performances. CONCLUSIONS: The capability of a first single TnI-Ultra level to exclude AMI from other myocardial injury in early and late presenters is poor. Addition of myoglobin assay offered no further improvement and was not considered useful.