What lab orders are appropriate for a patient presenting with chest pain?

Laboratory Orders for Chest Pain Evaluation

For patients presenting with chest pain, a comprehensive laboratory workup should include serial cardiac troponin measurements (preferably high-sensitivity troponin), with initial sample at presentation and repeat measurements at 1-3 hours for high-sensitivity troponin or 3-6 hours for conventional troponin assays. 1, 2

Initial Laboratory Assessment

Essential Laboratory Tests:

• Cardiac Troponin:
  • High-sensitivity cardiac troponin (hs-cTn) preferred over conventional troponin 1, 2
  • Initial sample at presentation (time zero)
  • Serial measurements at 1-3 hours for hs-cTn or 3-6 hours for conventional troponin 1, 2
  • A single hs-cTn below the limit of detection may exclude myocardial injury if symptoms began ≥3 hours before arrival 1

Additional Laboratory Tests:

• Complete Blood Count (CBC): To assess for anemia or infection
• Basic Metabolic Panel: To evaluate electrolyte abnormalities and renal function
• D-dimer: Consider if pulmonary embolism is suspected in patients with low to intermediate pre-test probability 2

Risk Stratification Approach

The laboratory workup should be guided by risk stratification of the patient into low, intermediate, or high-risk categories:

Low-Risk Patients (30-day risk of death or MACE <1%):

• May be discharged without admission or urgent cardiac testing if:
  • Normal ECG
  • Negative troponin values (below 99th percentile)
  • No concerning features on history/examination 1

Intermediate-Risk Patients:

• Serial troponin measurements are essential
• Consider additional testing based on clinical presentation

High-Risk Patients:

• Serial troponin measurements
• More aggressive diagnostic approach including possible invasive coronary angiography 1

Important Considerations

Troponin Testing Protocol:

• Institutions should implement a standardized clinical decision pathway that includes a protocol for troponin sampling based on their specific assay 1, 2
• Clinicians must be familiar with the specific assay used at their institution, including:
  • 99th percentile upper reference limit
  • Analytical precision
  • Sex-specific thresholds 2

Common Pitfalls to Avoid:

• Relying solely on a single troponin measurement instead of serial measurements 2
• Using outdated biomarkers such as CK-MB and myoglobin when troponin is available 2
• Misinterpreting troponin elevations, as elevations can occur in numerous cardiac and non-cardiac conditions 2
• Failing to incorporate previous testing results when available 1

Clinical Decision Pathways:

Several validated clinical decision pathways can help risk-stratify patients:

• HEART Pathway (History, ECG, Age, Risk Factors, Troponin)
• EDACS (Emergency Department Acute Coronary Syndrome)
• ADAPT (2-hour Accelerated Diagnostic Protocol) 1, 3

By implementing this structured laboratory testing approach based on risk stratification, clinicians can effectively evaluate patients with chest pain while optimizing resource utilization and ensuring patient safety.