From the Guidelines
Serial troponin testing should be performed over a 3-6 hour period to effectively rule out active myocardial ischemia, with the optimal approach being to obtain baseline troponin levels upon patient presentation, followed by repeat measurements at 3 hours and, if necessary, at 6 hours, as recommended by the 2017 AHA/ACC clinical performance and quality measures for adults with ST-elevation and non-ST-elevation myocardial infarction 1.
Key Considerations
- High-sensitivity troponin assays may allow for a shorter protocol (0 and 3 hours), while conventional assays typically require the full 6-hour window.
- The serial testing strategy helps identify the characteristic rise and/or fall pattern of troponin levels that distinguishes acute myocardial injury from chronic elevation.
- For patients with a low pre-test probability and negative initial troponin, a single repeat test at 3 hours may be sufficient, while those with higher risk or equivocal results should complete the full 6-hour protocol.
- Clinical context remains essential, as troponin elevation can occur in conditions other than acute coronary syndrome, including renal failure, sepsis, and pulmonary embolism.
Rationale
The 2017 AHA/ACC guideline recommends serial cardiac troponin I or T levels be obtained at presentation and 3 to 6 hours after symptom onset in all patients who present with symptoms consistent with ACS to identify a rising and/or falling pattern of values 1. This approach is supported by the 2014 AHA/ACC guideline for the management of patients with non-ST-elevation acute coronary syndromes, which also recommends measuring cardiac-specific troponin levels at presentation and 3 to 6 hours after symptom onset 1.
Important Notes
- The time of presentation should be considered the time of onset for assessing troponin values if the time of symptom onset is ambiguous 1.
- Additional troponin levels should be obtained beyond 6 hours after symptom onset in patients with normal troponin levels on serial examination when electrocardiographic changes and/or clinical presentation confer an intermediate or high index of suspicion for ACS 1.
From the Research
Serial Troponin Measurements for Ruling Out Active Ischemia
- The use of highly sensitive troponin (hsTn) assays can help in the rapid and efficient evaluation of suspected acute coronary syndrome (ACS) 2.
- Serial cardiac biomarker measurements, including hs-cTn levels, are important in clinical decision-making for patients with suspected ACS 3.
- For exclusion of myocardial infarction using hsTn assays, various protocols are available, including instant rule-out with undetectable hsTn levels at admission or normal hsTn/cTn levels combined with normal copeptin levels, or rule-out with serial controls of hsTn after 1,2, or 3 hours 4.
Time Period for Serial Troponin Measurements
- A study found that serial high-sensitivity cardiac troponin T measurements can rule out acute myocardial infarction with a sensitivity of 96.7% (95% confidence interval: 92.3-99.3) using a cut-off of <14 ng/l 5.
- Another study presented a one-hour algorithm with a baseline high-sensitivity cardiac troponin T value <12 ng/l and delta 1 hour <3 ng/l, which classified 60.2% of patients as rule-out with a summary sensitivity of 98.9% (96.4-100) 5.
- The optimal time period for serial troponin measurements is not explicitly stated, but studies suggest that measurements can be taken at admission and after 1,2, or 3 hours to rule out acute myocardial infarction 4, 5.
Clinical Implications
- The use of hsTn assays and serial troponin measurements can help reduce the time to diagnosis and discharge in patients with suspected ACS 2, 5.
- Clinicians should understand the value of serial cardiac biomarker measurements and how to incorporate hsTn levels into clinical decision-making to strengthen disposition decisions and safely discharge patients from the emergency department 3.