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 cardiac troponin measurements (preferably high-sensitivity troponin) and a 12-lead ECG, supplemented by a chest radiograph to evaluate for alternative causes of symptoms. 1

Initial Assessment and Risk Stratification

Immediate Testing

• 12-lead ECG: Should be performed within the 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
• Cardiac biomarkers:
  • High-sensitivity cardiac troponin (hs-cTn): Preferred over conventional troponin 1
  • Initial sample at presentation (time zero)
  • Serial measurements at specific intervals:
    • High-sensitivity troponin: Repeat at 1-3 hours
    • Conventional troponin: Repeat at 3-6 hours 1
• Chest radiograph: To evaluate for other cardiac, pulmonary, and thoracic causes of symptoms 1

Important Considerations for Troponin Testing

• Clinicians must be familiar with the specific assay used at their institution, including:
  • The 99th percentile upper reference limit
  • Analytical precision
  • Sex-specific thresholds 1
• 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
• With high-sensitivity troponin assays, CK-MB and myoglobin are not useful and should not be ordered 1

Clinical Decision Pathways (CDPs)

Institutions should implement a standardized clinical decision pathway that:

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

Additional Testing Based on Clinical Suspicion

For Suspected Pulmonary Embolism

• D-dimer testing (if low to intermediate pre-test probability)
• Consider further imaging if D-dimer is elevated or pre-test probability is high

For Suspected Aortic Pathology

• No specific laboratory tests are diagnostic
• Proceed directly to appropriate imaging

Common Pitfalls to Avoid

• Relying solely on a single troponin measurement: Serial measurements are essential to detect a rising or falling pattern indicative of acute myocardial injury 1
• Using outdated biomarkers: CK-MB and myoglobin do not add value when troponin is available 1
• Misinterpreting troponin elevations: Troponin is organ-specific but not disease-specific; elevations can occur in numerous cardiac and non-cardiac conditions 1
• Delaying ECG: Should be performed within 10 minutes of presentation and repeated if symptoms persist or change 1
• Overlooking the value of previous test results: Prior cardiac testing should be incorporated into the evaluation 1

By following this systematic laboratory approach, clinicians can efficiently risk-stratify patients with chest pain and determine appropriate next steps in management to reduce morbidity and mortality.