MI Diagnosis Using High-Sensitivity Troponin I 1-Hour Algorithm
What are the test characteristics of an algorithm to diagnose acute myocardial infarction (AMI) using a high-sensitivity troponin I (hs-TnI) assay with a new cutoff level of 6 ng/L?
This was an analysis of data from the prospective Biomarkers in Acute Cardiac Care study. A total of 1,040 patients with suspected acute coronary syndrome without ST-elevation (17.7% with MI) were enrolled in this single-center study in Germany. The authors offered the exclusion of non–ST-segment elevation MI (NSTEMI) defined by a TnI level <6 ng/L at admission, 1 hour following admission, and after 3 hours. Follow-up mortality was reported 12 months after admission. Results were validated in two independent cohorts, ADAPT and APACE.
With application of the TnI cutoff value of 6 ng/L, the rule-out algorithm demonstrated a high negative predictive value of 99.8% (95% confidence interval, 98.6%-100.0%) after 1 hour for NSTEMI. This was similar to that with a 3-hour approach.
A 1-hour diagnostic algorithm to diagnose AMI using a hs-TnI assay with a cutoff value of 6 ng/L has a very high negative predictive and performs very similar to a 3-hour approach.
This is an important study that lends support to an accelerated diagnostic protocol, incorporating hs-Tn testing in the emergency department in select patients. Nonetheless and as summarized in an accompanying editorial by Dr. David Morrow, “Because hs-Tn assays are not available in the United States, serial testing at presentation and 3 to 6 hours with a contemporary sensitive assay remains the US standard of care.”
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