From the Guidelines
The troponin I high sensitivity level of <3 ng/L is normal, as it falls well below the reference range of <18 ng/L, indicating no evidence of heart muscle damage or injury, as supported by the most recent guidelines 1. This result suggests that the heart is healthy and functioning normally. Troponin is a protein released into the bloodstream when heart muscle cells are damaged, such as during a heart attack.
- A low level like this does not require specific treatment or medication based on this result alone.
- If this test was ordered due to symptoms like chest pain or shortness of breath, those symptoms should be evaluated separately despite the normal troponin result, as other cardiac or non-cardiac conditions could be responsible, as recommended by the guidelines 1.
- Regular heart health maintenance through a balanced diet, regular exercise, not smoking, and managing conditions like high blood pressure or diabetes remains important for ongoing cardiovascular health. The diagnosis of myocardial infarction requires a rise and/or fall of troponin values, and a single elevated value above the decision level is required, as stated in the guidelines 1 and 1.
- The use of high-sensitivity assays allows for more sensitive detection of myocardial injury, and the values for the 99th percentile URL can be found in the package inserts for the assays or in recent publications 1.
- It is essential to distinguish acute causes of troponin elevation, which require a rise and/or fall of troponin values, from chronic elevations that tend not to change acutely, as noted in the guidelines 1.
From the Research
Troponin I, High Sensitivity
- The given Troponin I level is <3 ng/L, which is below the reference range of <18 ng/L.
- According to the study by 2, low high-sensitivity cardiac troponin T (hs-cTnT) thresholds on presentation can rule out acute myocardial infarction (AMI), and more than one-third of patients had presenting hs-cTnT concentrations below the limit of detection (5 ng/L), which was 94.4% sensitive for 30-day major adverse cardiac events (MACE).
- The study by 3 found that stress echocardiography is superior to exercise electrocardiography in discriminating between patients with a low and intermediate risk of coronary artery disease (CAD) and correctly identified patients with significant CAD.
- The study by 4 described the variation in troponin I measurement and the cardiovascular diagnostic and therapeutic approach to elevated troponin I among critically ill adults with sepsis, and found that troponin I measurement and the approach to an elevated troponin I varied widely across hospitals.
- The study by 5 systematically reviewed the literature regarding the use of medications known to reduce mortality in patients with cardiac troponin elevation due to type I myocardial infarction (MI) in studies of critically ill patients without type I MI, and found that β blockers, statins, and aspirin may play a role in reducing mortality in non-cardiac critically ill patients.
- The study by 6 found that a 2-hour accelerated protocol using high sensitivity Troponin assay at 0 and 2 hours with comprehensive clinical evaluation and ECG followed by stress testing may be successful in identifying low-risk patient population who may benefit from early discharge from the emergency department.
Clinical Implications
- The results of these studies suggest that low levels of Troponin I, such as <3 ng/L, may indicate a low risk of cardiac events, and that further risk stratification may not be necessary in the absence of high-risk clinical presentation.
- Stress testing, such as exercise treadmill stress test or nuclear stress test, may be used to further evaluate patients with low Troponin I levels and non-diagnostic ECG.
- The use of high sensitivity Troponin assays and accelerated diagnostic protocols may help to reduce unnecessary admissions and testing, and improve patient outcomes.