Troponin Trending in Suspected Acute Coronary Syndrome
Cardiac-specific troponin (troponin I or T) should be measured at presentation and 3-6 hours after symptom onset in all patients with suspected acute coronary syndrome (ACS) to identify a rising and/or falling pattern. 1, 2
Initial Troponin Measurement Protocol
- Measure cardiac-specific troponin at presentation (baseline)
- Repeat measurement 3-6 hours after symptom onset
- If symptom onset time is unclear or ambiguous, consider the time of presentation as the time of symptom onset 1, 2
Extended Troponin Measurement Protocol
- For patients with initially normal troponin values but with concerning ECG changes or intermediate/high-risk clinical features, obtain additional troponin levels beyond 6 hours 1, 2
- The goal is to identify a rising and/or falling pattern with at least one value above the 99th percentile of the upper reference level 1
Interpretation of Troponin Values
- For diagnosis of acute myocardial necrosis, determine both peak troponin value and serial changes:
- A troponin value above the 99th percentile of the upper reference level is required
- Evidence for a serial increase or decrease ≥20% is required if the initial value is elevated
- For values below or close to the 99th percentile, a change of ≥3 standard deviations indicates acute myocardial necrosis 1
Special Considerations
- For patients presenting >24 hours after symptom onset, the rising/falling pattern may not be as evident 2
- In patients with renal failure, chronic heart failure, or other conditions, troponin may be chronically elevated, requiring careful interpretation of results 2
- For suspected reinfarction, an immediate measurement followed by a second sample 3-6 hours later is recommended, with ≥20% increase indicating recurrent infarction 2
Prognostic Assessment
- The presence and magnitude of troponin elevations provide important prognostic information 1
- It may be reasonable to remeasure troponin once on day 3 or day 4 in patients with confirmed MI as an index of infarct size 1
Common Pitfalls to Avoid
- Do not rely solely on a single troponin measurement for diagnosis or exclusion of ACS
- Do not use creatine kinase myocardial isoenzyme (CK-MB) or myoglobin for diagnosis of ACS as they are not useful with contemporary troponin assays 1
- Do not assume isolated troponin elevations are always due to ACS, as they can occur in other conditions such as tachyarrhythmias, heart failure, myocarditis, pulmonary embolism, sepsis, or renal failure 2
By following this evidence-based approach to troponin trending, clinicians can optimize the diagnosis of ACS while minimizing unnecessary testing and hospital stays.