Troponin levels pass diagnostic threshold in 25% of patients with STEMI
Among patients with STEMI, 1 in 4 had troponin concentrations less than the European Society of Cardiology-recommended rule-in threshold for accelerated diagnostic testing at presentation, researchers reported.
Although patients who presented within 2 hours of symptom onset were more likely to have concentrations less than the 99th percentile, just 1 in 6 had troponin concentrations less than the diagnostic threshold (5 ng/L).
“During myocardial infarction, abrupt coronary occlusion may prevent the release of troponin into the circulation until reperfusion has occurred,” Ryan Wereski, MD, clinical research fellow at the BHF Centre for Cardiovascular Science at the University of Edinburgh, Scotland, and colleagues wrote. “Our observations are an important reminder of the limited role of troponin testing in the early assessment of patients with ST-segment elevation.”
For this research letter published in JAMA Cardiology, investigators recruited 48,282 consecutive patients (925 with adjudicated diagnosis of STEMI; 68% men; mean age, 65 years) from June 2013 to March 2016 with suspected ACS from 10 centers included in the High-STEACS randomized trial. High-sensitivity troponin was measured using an assay (Architect Stat, Abbott Laboratories) with a detection limit of 1.2 ng/L and a 99th percentile upper reference limit of 34 ng/L for men and 16 ng/L for women.
According to the letter, patients with type 1 STEMI were stratified based on troponin concentration at presentation using the diagnostic threshold, sex-specific 99th percentile and the ESC 0 of 1-hour pathway rule-in diagnostic threshold (52 ng/L).
Median troponin concentration at presentation was 196 ng/L, with 2.2% of patients having troponin concentrations less than 5 ng/L, 14.4% with concentrations in the 99th percentile and 73.2% with concentrations greater than the ESC rule-in diagnostic threshold.
Moreover, patients who presented within 2 hours of symptom onset had lower troponin concentrations (96 ng/L vs. 294 ng/L; P < .001) and were more likely to have concentrations less than the 99th percentile (26.4% vs 14.1%; P < .001) compared with patients who presented after more than 2 hours.
“Where clinical suspicion is high, troponin concentrations within the reference range should not delay the initiation of therapeutic agents or urgent coronary angiography,” the researchers wrote. “This is particularly relevant in patients with electrocardiographic changes suspicious of posterior myocardial infarction, but our findings are relevant to a wider group of patients with conduction abnormalities, such as bundle branch block or ventricular pacing, where interpretation of the electrocardiogram is challenging.”