From the Guidelines
Troponin I and troponin T are both recommended for diagnosing acute coronary syndromes, with the choice between them depending on laboratory capabilities and protocols, as stated in the 2014 AHA/ACC guideline 1. When considering the diagnosis of acute coronary syndromes (ACS), both troponin I and troponin T are cardiac-specific biomarkers that can be used to identify myocardial injury.
- The key difference between troponin I and troponin T lies in their specificity to cardiac tissue, with troponin I being more specific due to its minimal expression in skeletal muscle.
- Troponin T, while also cardiac-specific, may be elevated in certain non-cardiac conditions, which could potentially lead to false positives in some cases. The 2014 AHA/ACC guideline for the management of patients with non-ST-elevation acute coronary syndromes recommends measuring cardiac-specific troponin (troponin I or T) levels at presentation and 3 to 6 hours after symptom onset to identify a rising and/or falling pattern 1.
- This guideline suggests that both troponin I and troponin T can be used effectively for the diagnosis of ACS when contemporary assays are utilized. In terms of their clinical application, the choice between troponin I and troponin T often comes down to the specific capabilities and protocols of the hospital laboratory, rather than significant differences in diagnostic accuracy.
- Both biomarkers have similar sensitivity for detecting myocardial injury in most situations, making them equally valuable for diagnosing ACS. It's essential for clinicians to interpret troponin results according to their institution's established cutoff values, as these can vary by laboratory and assay method.
- By following the recommendations outlined in the 2014 AHA/ACC guideline and considering the specific characteristics of troponin I and troponin T, clinicians can effectively diagnose and manage patients with acute coronary syndromes 1.
From the Research
Comparison of Troponin I and Troponin T
- Troponin I and Troponin T are both cardiac-specific biomarkers used for the diagnosis of acute myocardial infarction (AMI) 2, 3.
- Studies have shown that both troponin I and troponin T have good sensitivity and specificity as indicators of myocardial necrosis, and are superior to other biomarkers such as creatine kinase (CK) and its MB isoenzyme (CK-MB) 2.
- The sensitivity and specificity of troponin T and I vary depending on the time from onset of symptoms, with sensitivity increasing and specificity declining over time 3.
Diagnostic Thresholds and Kinetics
- The 99th percentile is the recommended diagnostic threshold for myocardial infarction, but higher troponin thresholds may be used to rule in myocardial infarction at presentation 4.
- The kinetics of troponin concentration, including absolute, relative, and rate of change, can help differentiate type 1 myocardial infarction from other causes of myocardial injury or infarction 4, 5.
- Maximum troponin levels have been shown to be a more sensitive and specific predictor of mortality and diagnosis of AMI than initial or change in troponin level 6.
Clinical Applications
- Troponin I and troponin T are useful tools for the diagnosis of AMI, but must be interpreted according to the number of hours from the onset of chest pain 3.
- High-sensitivity troponin assays have improved diagnostic sensitivity for earlier detection of MI, but have also increased the detection of myocardial injuries in non-ACS conditions 5.
- Even minor elevations in troponin levels provide important prognostic information, and increased levels of troponin are associated with adverse outcomes in both ACS and non-ACS conditions 5, 6.