Early Dynamic Change in High-Sensitivity Cardiac Troponin T in the Investigation of Acute Myocardial Infarction

Study Questions:

Does assessment of serial changes in high-sensitivity troponin T (hs-TnT) improve diagnostic and prognostic test performance in the emergency department patients with possible acute myocardial infarction (AMI)?

Methods:

A total of 939 patients with possible myocardial ischemia without ST elevation were included, and hs-cTnT was measured at 0 and 2 hours after presentation. Endpoints included admission diagnosis of AMI and 1-year adverse events (composite of death, AMI, and revascularization).

Results:

AMI was diagnosed in 200 patients, and 111 patients had late events. Using the 99th percentile had a specificity of 80% (95% confidence interval, 78.8%-80.5%). Specificity improved to 94% (92.9%-95.4%) when a delta change ≥20% from 0 to 2 hours was also included. However, this significantly reduced sensitivity from 94.5% (90.7%-96.9%) to 50% (44.6%-53.9%). In patients who had a 0- to 2-hour hs-cTnT <99th percentile, including those patients with a delta change ≥20% sensitivity increased to 97.5% (94.4%-98.9%), and limited the decrease in specificity to 65% (64%-65%). An hs-cTnT ≥99th percentile predicted late adverse events, with an adjusted hazard ratio of 1.9 (1.2-2.8); in contrast, a delta change ≥20% did not (hazard ratio, 1.1 [0.7-1.7]).

Conclusions:

Diagnostic specificity of hs-cTnT improved when a delta change ≥20% was used in addition to the ≥99th percentile, at a cost of a substantial reduction in sensitivity. Limiting use of a delta change ≥20% to patients with 0- to 2-hour concentrations <99th percentile significantly improved sensitivity, with less decrease in specificity. Both approaches may be required for optimum rule-in and rule-out strategies, respectively. An absolute rather than delta change in hs-cTnT was predictive of long-term events.

Perspective:

This is an interesting paper indicating that the use of a rising pattern of values using a change criteria of 20% with the hs-cTnT assay improves specificity for the diagnosis of AMI, but at the expense of sensitivity. This trade-off was less apparent in patients presenting early than in those presenting late. These data likely are realistic and depict an important trade-off that clinicians should be aware of. It is unclear, however, if 20% or some other metric is the best percentage change to use or indeed whether other approaches such as an absolute change might be better.

Keywords: Incidence, Prognosis, Coronary Artery Disease, Myocardial Infarction, Myocardial Ischemia, Cytoskeletal Proteins, Death, Biological Markers, Cardiology, Cardiovascular Diseases, Troponin T


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