From the Guidelines
High-sensitive troponin (hs-troponin) levels are considered normal when they are below 14 ng/L for hs-cTnT and 26 ng/L for hs-cTnI at 0 and 3 hours, according to the most recent guidelines 1. The normal range for high-sensitive troponin can vary slightly between laboratories and assay types, but these values are generally accepted as the cutoff for ruling out myocardial infarction (MI) in patients presenting with symptoms of acute coronary syndrome. Some key points to consider when interpreting hs-troponin results include:
- Even small elevations above the normal range can indicate cardiac damage
- Serial measurements are often more valuable than single readings, as a rising or falling pattern provides more diagnostic information than an isolated value
- Non-cardiac conditions like renal failure, sepsis, and pulmonary embolism can also cause troponin elevation without acute coronary syndrome
- High-sensitivity troponin assays can detect very small amounts of the protein, allowing for earlier detection of myocardial injury and more rapid rule-out of myocardial infarction in appropriate clinical settings The 2019 guidelines from the Journal of the American College of Cardiology provide a summary of the rule-out and rule-in criteria for MI using hs-cTnT and hs-cTnI, including the cutoff values and the negative predictive value (NPV) and positive predictive value (PPV) for each assay 1. In contrast, the 2014 AHA/ACC guideline for the management of patients with non-ST-elevation acute coronary syndromes recommends using the 99th percentile of the upper reference level as the cutpoint for considering myocardial necrosis, and provides guidance on the interpretation of serial changes in troponin values 1. However, the most recent and highest quality study, which is the 2019 guideline, should be prioritized when making clinical decisions about hs-troponin interpretation 1.
From the Research
Normal Range for High-Sensitive Troponin (hs-troponin)
- The normal range for high-sensitive troponin (hs-troponin) is generally considered to be below the 99th percentile upper reference limit 2, 3.
- Studies have shown that the 99th percentile for hs-troponin can vary depending on factors such as age, sex, and renal function 3.
- For example, one study found that the 99th percentile for hs-cTnT among all men and among women <50 years of age with normal renal function was 20 and 12 ng/L, respectively, and increased to 44 and 36 ng/L, respectively, at the age of 70-79 years 3.
- Another study found that a hs-TnI cutoff of 3 ng/L resulted in a negative predictive value (NPV) of 99.3% for ruling out acute myocardial infarction (AMI) 4.
- The European Society for Cardiology (ESC) recommends using a second hsTnT measurement 3 hours later to distinguish between ACS and other causes depending on the Δ hsTnT, with a cut-off value of 14-51 ng/L representing a challenge in diagnosing acute coronary syndrome (ACS) 5.
Factors Affecting hs-troponin Levels
- Age: older patients tend to have higher hs-troponin levels than younger patients 3.
- Sex: men tend to have higher hs-troponin levels than women 3.
- Renal function: reduced estimated glomerular filtration rate (eGFR) is a strong predictor of elevated hs-troponin levels 3.
- Comorbidities: presence of comorbidities such as chronic cardiovascular conditions can affect hs-troponin levels 6.