What lab workup is indicated for a patient presenting with chest pain?

Laboratory Workup for Chest Pain

The essential laboratory workup for a patient presenting with chest pain should include serial high-sensitivity cardiac troponin measurements and a 12-lead ECG performed within the first 10 minutes of presentation, supplemented by a chest radiograph to evaluate for alternative causes of symptoms. 1

Initial Assessment

Core Laboratory Tests

• High-sensitivity cardiac troponin (hs-cTn):

  • Initial sample at presentation (time zero)
  • Serial measurements at specific intervals:
    • High-sensitivity troponin: 1-3 hours after initial sample
    • Conventional troponin: 3-6 hours after initial sample 1
  • Note: Be familiar with your institution's specific assay, including the 99th percentile upper reference limit, analytical precision, and sex-specific thresholds

• 12-lead ECG:

  • Must be performed within first 10 minutes of presentation
  • Look for ST-segment elevation/depression, T-wave inversions, or new left bundle branch block
  • Consider supplemental leads V7-V9 if posterior MI is suspected 1

• Chest radiograph:

  • Helps evaluate for alternative causes of chest pain (pneumonia, pneumothorax, etc.) 1

Risk Stratification

Implement a standardized clinical decision pathway that:

• Categorizes patients into low, intermediate, and high-risk strata
• Includes protocol for troponin sampling based on specific assay used
• Incorporates previous cardiac testing results when available 1

Special Considerations

• For patients with chest pain, normal ECG, and symptoms beginning ≥3 hours before arrival, a single hs-cTn below the limit of detection may reasonably exclude myocardial injury 1
• D-dimer testing may be considered if low to intermediate pre-test probability for pulmonary embolism 1

Additional Testing Based on Clinical Suspicion

When ACS is ruled out, consider laboratory tests for alternative diagnoses:

• Pulmonary embolism: D-dimer (if low-intermediate pretest probability)
• Aortic dissection: No specific laboratory test; proceed directly to imaging
• Pericarditis/myocarditis: Consider inflammatory markers (ESR, CRP)

Common Pitfalls to Avoid

1. Relying on a single troponin measurement: Serial measurements are essential to detect a rising or falling pattern indicative of acute myocardial injury 1

2. Using outdated biomarkers: CK-MB and myoglobin do not add value when troponin is available 1

   • Research shows that adding BNP to troponin, CK-MB, and myoglobin increases sensitivity at the cost of decreased specificity for acute myocardial infarction 2
   • More recent evidence indicates that in patients evaluated using high-sensitivity troponin, NT-proBNP does not contribute additional predictive value 3

3. Misinterpreting troponin elevations: Troponin is organ-specific but not disease-specific; elevations can occur in numerous cardiac and non-cardiac conditions 1

4. Delaying ECG: This can significantly impact patient management and outcomes 1

5. Overlooking previous test results: Incorporating previous cardiac testing results is important for proper risk stratification 1