From the Guidelines
The troponin I high sensitivity result of <3 ng/L is normal, indicating no evidence of heart muscle damage at this time, as values above the 99th percentile of the upper reference level are required for consideration of myocardial necrosis 1. This normal result should be interpreted in the context of the overall clinical picture, including symptoms, other test results, and risk factors. Key points to consider include:
- Troponin is a protein released into the bloodstream when heart muscle cells are damaged, such as during a heart attack 1.
- High-sensitivity troponin tests can detect very small amounts of this protein, allowing for earlier detection of heart injury.
- A value below 3 ng/L is considered within the normal range and suggests that there is no ongoing cardiac injury.
- Serial measurements are often performed (typically at 0,3, and 6 hours) to detect any changing patterns that might indicate developing heart damage, as evidence for a serial increase or decrease ≥20% is required if the initial value is elevated 1. Some important considerations when interpreting troponin results include:
- Solitary elevations of troponin cannot be assumed to be due to MI, because troponin elevations can be due to other conditions such as tachyarrhythmia, hypotension or hypertension, cardiac trauma, acute HF, myocarditis and pericarditis, acute pulmonary thromboembolic disease, and severe noncardiac conditions 1.
- Chronic elevations can result from structural cardiac abnormalities such as LV hypertrophy or ventricular dilatation and are also common in patients with renal insufficiency 1. If you're experiencing symptoms like chest pain, shortness of breath, or other concerning symptoms, it's essential to continue monitoring as troponin levels may rise over time following cardiac injury, and clinical laboratory reports should indicate whether significant changes in cardiac troponin values for the particular assay have occurred 1.
From the Research
Troponin I, High Sensitivity
Overview of Studies
- The studies examined the use of high-sensitivity troponin I (hs-TnI) to rule out acute myocardial infarction (AMI) in patients presenting with suspected AMI.
- The results showed that a single hs-TnI measurement on admission, combined with a low-risk electrocardiogram (ECG), can safely rule out AMI without the need for serial troponin testing 2.
- A hs-TnI cutoff of 3 ng/L resulted in a negative predictive value (NPV) of 99.3% (CI 97.3-100.0), ruling out 35% of all non-AMI patients 2.
Low-Risk Patients
- Low high-sensitivity troponin thresholds can identify low-risk patients with chest pain who are unlikely to benefit from further risk stratification 3.
- Patients with hs-TnI concentrations below the limit of detection (5 ng/L) had a low risk of 30-day major adverse cardiac events (MACE) 3.
- A cardiac troponin I concentration of less than 5 ng/L identified patients at low risk of myocardial infarction or cardiac death within 30 days 4.
Point-of-Care Testing
- A rapid point-of-care (POC) whole-blood hs-cTnI assay can be used to rule out AMI at low risk, with a negative predictive value of ≥99.5% and sensitivity of >99% for index MI 5.
- A POC whole-blood hs-cTnI concentration of <4 ng/L provided a sensitivity of 98.9% (95% CI, 93.8%-100%) and negative predictive value of 99.5% (95% CI, 97.2%-100%) for ruling out MI 5.
Clinical Utility
- A baseline high-sensitivity cardiac troponin I level below the limit of quantitation can rule out acute myocardial infarction in the emergency department 6.
- A baseline presenting novel hs-cTnI value of <4.0 ng/L effectively ruled out AMI in 40.9% of all patients presenting to the ED and having any symptoms suspicious for AMI 6.