From the Guidelines
Troponin testing should be ordered when evaluating patients with suspected acute coronary syndrome (ACS), including myocardial infarction, specifically for patients presenting with chest pain, shortness of breath, jaw or arm pain, or other symptoms suggestive of cardiac ischemia, as recommended by the 2017 AHA/ACC guideline 1. The standard approach involves obtaining an initial troponin level upon presentation and a second measurement 3-6 hours later, with some high-sensitivity assays allowing for shorter intervals of 1-3 hours, as stated in the 2014 AHA/ACC guideline for the management of patients with non-ST-elevation acute coronary syndromes 1. Some key points to consider when ordering troponin tests include:
- Measuring cardiac-specific troponin (troponin I or T) at presentation and 3–6 h after symptom onset in all patients with suspected ACS to identify a pattern of values 1
- Obtaining additional troponin levels beyond 6 h in patients with initial normal serial troponins with electrocardiographic changes and/or intermediate/high risk clinical features 1
- Considering the time of presentation as the time of onset for assessing troponin values when the time of symptom onset is ambiguous 1
- Using the 99th percentile of the upper reference level as the appropriate cutpoint for considering myocardial necrosis, and determining not only the peak troponin value but also serial changes 1 Additional indications for troponin testing include monitoring patients after cardiac procedures, evaluating non-specific symptoms in high-risk patients (elderly, diabetics), and assessing patients with heart failure exacerbations, pulmonary embolism, or after significant non-cardiac surgery. Troponin is a cardiac-specific protein released when heart muscle cells are damaged, making it highly sensitive and specific for myocardial injury, as noted in the 2015 international consensus on cardiopulmonary resuscitation and emergency cardiovascular care science with treatment recommendations 1. However, elevated troponin doesn't always indicate ACS, as it can also rise in conditions like myocarditis, sepsis, renal failure, and pulmonary embolism, therefore clinical context must always guide interpretation of results.
From the Research
When to Order Troponin
Troponin is a cardiac biomarker used to diagnose acute myocardial infarction (AMI) and assess cardiac damage. The decision to order troponin depends on various factors, including the patient's symptoms, medical history, and electrocardiogram (ECG) results.
- Symptoms suggestive of AMI: Troponin should be ordered in patients with symptoms suggestive of AMI, such as chest pain, shortness of breath, or fatigue, especially if they have a history of coronary artery disease or risk factors for cardiovascular disease 2, 3.
- ECG results: Troponin should be ordered in patients with non-diagnostic or normal ECG results, as it can help diagnose AMI in these cases 4, 5.
- Timing of troponin measurement: Troponin levels can be measured at presentation, and serial measurements can be taken 3-6 hours after admission to improve diagnostic accuracy 2, 3.
- High-sensitivity troponin assays: High-sensitivity troponin assays can detect lower levels of troponin, allowing for earlier diagnosis of AMI and improved risk stratification 5, 3.
- Low troponin levels: Even low levels of troponin (e.g., > 0.03 μg/L) can indicate an increased risk of future complications, and patients with these levels should be closely monitored 6.
Clinical Considerations
When ordering troponin, clinicians should consider the following:
- Clinical presentation: Troponin should be ordered in patients with symptoms suggestive of AMI, regardless of the ECG results.
- Risk factors: Patients with risk factors for cardiovascular disease, such as hypertension, diabetes, or hyperlipidemia, should be considered for troponin measurement.
- Serial measurements: Serial troponin measurements can help improve diagnostic accuracy and monitor disease progression.
- Assay sensitivity: High-sensitivity troponin assays can detect lower levels of troponin, allowing for earlier diagnosis and improved risk stratification.