Single high-sensitivity troponin I test below 2 ng/L rules out MI in early presenters
Key takeaways:
- A single high-sensitivity troponin I test below 2 ng/L could be enough to rule out MI in early presenters.
- Sex-specific 99th percentile thresholds showed lower predictive value and were not recommended.
One high-sensitivity cardiac troponin I measurement under the limit of detection — 2 ng/L — may be enough to rule out MI with high sensitivity among patients who present within 12 hours of symptom onset, researchers reported.
Sex-specific 99th percentile thresholds for high-sensitivity cardiac troponin I — 16 ng/L for women and 34 ng/L for men — demonstrated low predictive value to rule out MI among both early and late presenters with suspected MI, according to data published in the European Heart Journal.
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“High-sensitivity cardiac troponin assays are able to quantify low levels of cardiac troponin in the majority of presumably healthy individuals ... However, concerns remain about the use of a single test strategy in early presenters, and it is unclear how the performance of cardiac troponin changes with time following symptom onset,” Matthew T. H. Lowry, MD, clinical research fellow at the British Heart Foundation center for cardiovascular science at the University of Edinburgh, U.K., and colleagues wrote. “Early rule-out thresholds use low levels of cardiac troponin to identify patients at presentation who are low risk and may not require serial testing ... In consecutive patients with suspected myocardial infarction, we aimed to evaluate and to validate externally the diagnostic performance of a single measurement of cardiac troponin I at presentation stratified according to the time of symptom onset.”
Initial evaluation of a single troponin I measure from a high-sensitivity assay (Architect Stat, Abbott) to rule out MI in early presenters was conducted using a derivation cohort from the High-STEACS randomized trial and was externally validated using data from the APACE Study.
High-sensitivity cardiac troponin I was evaluated among patients who presented within 3 hours, between 4 and 12 hours and more than 12 hours from symptom onset.
Lowry and colleagues compared three troponin I thresholds: limit-of-detection (2 ng/L), rule-out (5 ng/L) and sex-specific 99th percentile (16 ng/L in women; 34 ng/L in men).
The primary outcome was type 1 or 4b MI during index presentation.
High-sensitivity troponin I to rule out MI
Among 41,103 consecutive patients (mean age, 60 years; 46% women), 31% presented within 3 hours of symptom onset and 9% had MI.
Compared with 5 ng/L, the 2 ng/L high-sensitivity troponin I threshold had greater sensitivity (99.4% vs. 96.5%) and negative predictive value (99.7% vs. 99.3%) among patients who presented within 3 hours of symptom onset.
Among patients who presented 3 hours or more after symptom onset, the sensitivity and negative predictive value for the 2 ng/L and 5 ng/L thresholds were similar, according to the study.
Moreover, the sensitivity of the 99th percentile troponin I threshold to rule out MI was low for both early (71.4%) and late presenters (92.5%).
The results were consistent in an external validation using data from a cohort of 7,088 patients in the APACE Study.
Time from symptom onset matters
“The time from symptom onset to testing strongly influences the diagnostic performance of high-sensitivity cardiac troponin I to rule out myocardial infarction,” the researchers wrote. “A single measurement below the limit of detection enables myocardial infarction to be ruled out at presentation in those undergoing troponin testing within a few hours of symptom onset. In contrast, the 99th centile diagnostic threshold should not be used to rule out myocardial infarction at presentation even in those presenting 12 hours after symptom onset.”
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