Which type of troponin (cardiac biomarker) is recommended for evaluating suspected acute myocardial infarction?

High-Sensitivity Cardiac Troponin Is the Recommended Troponin Type for Evaluating Suspected AMI

High-sensitivity cardiac troponin (hs-cTn) assays, either troponin T (hs-cTnT) or troponin I (hs-cTnI), are strongly recommended over conventional troponin assays for evaluating suspected acute myocardial infarction. 1

Advantages of High-Sensitivity Cardiac Troponin Assays

High-sensitivity cardiac troponin assays offer several important clinical advantages:

• Superior diagnostic accuracy: hs-cTn assays provide higher diagnostic accuracy at identical low cost compared to conventional assays 1
• Earlier detection: They can detect myocardial injury much earlier after symptom onset (usually within 1 hour) 1
• Improved sensitivity: hs-cTn assays can detect troponin in 50-95% of healthy individuals, allowing for better discrimination between normal and abnormal values 1
• Reduced time to diagnosis: The use of hs-cTn enables shorter diagnostic algorithms (0h/1h or 0h/2h), reducing emergency department stays and costs 1
• Comparable performance: Both hs-cTnT and hs-cTnI assays provide similar diagnostic accuracy for early MI diagnosis 1

Diagnostic Algorithm Using High-Sensitivity Troponin

The European Society of Cardiology recommends the following approach when using hs-cTn:

1. Initial measurement: Obtain hs-cTn immediately at presentation (0h)
2. Follow-up measurement: Repeat at 1h (preferred) or 2h (second-best option) 1
3. Additional testing: If the first two measurements are inconclusive and clinical suspicion remains high, obtain an additional measurement at 3h 2
4. Interpretation: Look for a rising and/or falling pattern with at least one value above the 99th percentile upper reference limit 1

Interpretation of Results

When interpreting hs-cTn results:

• Quantitative assessment: Higher levels indicate greater likelihood of MI 1
• Significant elevations: Values >5-fold the upper reference limit have high (>90%) positive predictive value for acute type 1 MI 1
• Moderate elevations: Values up to 3-fold the upper reference limit have limited (50-60%) positive predictive value for AMI and may be associated with other conditions 1
• Serial changes: Rising/falling patterns help differentiate acute from chronic myocardial damage 1

Important Considerations and Pitfalls

Non-MI Causes of Troponin Elevation

Many conditions besides MI can cause elevated troponin levels, including:

• Tachyarrhythmias, heart failure, hypertensive emergencies
• Critical illness (shock/sepsis/burns)
• Myocarditis, Takotsubo syndrome
• Valvular heart disease, aortic dissection, pulmonary embolism
• Renal dysfunction and associated cardiac disease
• Acute neurological events 1

Technical Considerations

• Assay precision: Optimal precision at the 99th percentile URL should be defined as ≤10% coefficient of variation 1
• Point-of-care tests: Most currently used point-of-care tests cannot be considered sensitive or high-sensitivity assays 1
• Sex-specific reference ranges: Consider using sex-differentiated 99th percentile values for improved diagnostic accuracy 3

Comparison with Other Cardiac Biomarkers

• CK-MB and myoglobin: With contemporary troponin assays, CK-MB and myoglobin are not useful for the diagnosis of ACS 1
• B-type natriuretic peptide (BNP): May provide additional prognostic information but is not recommended for primary diagnosis of AMI 1

Conclusion

For optimal evaluation of suspected acute myocardial infarction, high-sensitivity cardiac troponin assays (either hs-cTnT or hs-cTnI) are the recommended biomarkers due to their superior diagnostic accuracy, earlier detection capabilities, and ability to implement rapid diagnostic algorithms. Proper interpretation requires understanding both the quantitative value and its change over time.