From the Guidelines
The threshold for an abnormal high-sensitivity troponin result is generally defined as the 99th percentile upper reference limit (URL) from a healthy reference population, with the most recent guidelines recommending the use of sex-specific thresholds. According to the latest evidence from 1, the 99th percentile upper reference limits are recommended as the threshold for myocardial injury and to support the diagnosis of MI. The use of sex-specific thresholds is also endorsed, with studies such as 1 demonstrating that sex-specific thresholds can lead to a more accurate diagnosis of myocardial infarction, particularly in women.
When interpreting high-sensitivity troponin results, it's essential to consider the following key points:
- The 99th percentile upper reference limit (URL) varies by assay type and laboratory
- Sex-specific cutoffs are increasingly used, with typical values around 16 ng/L for men and 10 ng/L for women for high-sensitivity troponin T (hs-cTnT) assays
- For high-sensitivity troponin I (hs-cTnI), the thresholds vary more widely between manufacturers, ranging from about 26 ng/L to 45 ng/L
- A significant increase in troponin levels over time (delta change) can indicate acute myocardial injury, even when values remain below the 99th percentile
- Troponin elevation can occur in conditions other than acute coronary syndromes, including heart failure, pulmonary embolism, myocarditis, and renal failure
As noted in 1, the European Society of Cardiology recommends the use of high-sensitivity cardiac troponin assays for the diagnosis of acute coronary syndromes, with a focus on the 99th percentile upper reference limit as the threshold for myocardial injury. Similarly, 1 emphasizes the importance of considering serial changes in troponin levels and the clinical context when interpreting results.
In clinical practice, the use of high-sensitivity troponin assays requires careful consideration of the assay-specific 99th percentile upper reference limit, as well as the patient's clinical presentation and medical history. By following the latest guidelines and recommendations, clinicians can optimize the diagnosis and management of patients with suspected acute coronary syndromes.
From the Research
Threshold for Abnormal Result on High Sensitivity Troponin Test
- The threshold for an abnormal result on a high sensitivity troponin test is typically defined as the 99th percentile upper reference limit (URL) 2.
- Studies have reported the following 99th percentile URLs for high-sensitivity cardiac troponin I (hs-cTnI) assays:
- A troponin level above the 99th percentile URL is considered abnormal and may indicate myocardial injury or infarction 4, 3, 2, 5.
- However, the use of higher troponin thresholds, such as 64 ng/L or 5-fold the upper reference limit, may be advocated to rule in myocardial infarction at presentation 5.
Factors Influencing Troponin Thresholds
- Sex: Men tend to have higher troponin levels than women 3, 2.
- Age: Older patients tend to have higher troponin levels than younger patients 3.
- Renal function: Reduced estimated glomerular filtration rate (eGFR) is a strong predictor of elevated troponin levels 3.
- Comorbidities: Presence of comorbidities, such as cardiovascular disease, may influence troponin levels 3.
Clinical Implications
- A high-sensitivity troponin level under the 99th percentile URL drawn at 6 hours or greater from symptom onset may safely rule out acute coronary syndrome in patients who do not meet rapid rule-out criteria 6.
- Troponin concentrations at presentation are insufficient to distinguish type 1 myocardial infarction from other causes of myocardial injury or infarction, and should not guide management decisions in isolation 5.