What laboratory tests are indicated for a patient presenting with chest pain?

Laboratory Tests for Chest Pain Evaluation

Cardiac troponin (cTn I or T) measurement is the essential laboratory test for all patients presenting with chest pain, with high-sensitivity troponin (hs-cTn) strongly preferred when available. 1, 2

Immediate Initial Testing

All patients with acute chest pain require:

• Cardiac troponin measurement as soon as possible after ED arrival 1, 2
• ECG within 10 minutes of arrival to evaluate for STEMI and ischemic changes 1
• Chest radiograph to evaluate for cardiac, pulmonary, and thoracic causes of symptoms 1, 2

Serial Troponin Protocols

The timing of repeat troponin measurements depends on the assay type used at your institution: 1, 2

• High-sensitivity troponin (hs-cTn): Repeat at 1-3 hours after initial sample
• Conventional troponin: Repeat at 3-6 hours after initial sample

For patients whose symptoms began ≥3 hours before ED arrival with normal ECG, a single hs-cTn below the limit of detection may reasonably exclude myocardial injury. 1, 2 However, serial measurements remain indicated when clinical suspicion is high, symptoms persist, or the patient's condition deteriorates. 1, 2

Critical Implementation Points

Your institution must have a standardized clinical decision pathway that specifies the troponin protocol based on your specific assay. 1, 2 You must know the 99th percentile upper reference limit that defines myocardial injury for your particular troponin assay. 1, 2

Obsolete Tests to Avoid

With cardiac troponin availability, CK-MB isoenzyme and myoglobin are NOT useful for diagnosing acute myocardial injury and should not be ordered. 1, 2 These older biomarkers have been superseded by troponin's superior sensitivity and specificity.

Additional Laboratory Considerations

While not part of routine chest pain evaluation, basic laboratory tests may be indicated based on clinical presentation: 1

• Hemoglobin to detect anemia that could precipitate demand ischemia 1
• Complete blood count for infection evaluation if pneumonia suspected 1
• D-dimer only if aortic dissection or pulmonary embolism is specifically suspected based on clinical features 1, 3

Risk-Stratified Approach

The troponin results combined with ECG findings and clinical features determine subsequent management: 1, 2

• Elevated troponin with rising/falling pattern: Indicates acute myocardial injury requiring immediate ACS management 1
• Normal serial troponins in low-risk patients (<1% 30-day MACE risk): Reasonable to discharge without admission 1, 2
• Intermediate-risk patients: May require observation unit management and additional cardiac testing 1

Office Setting Pitfall

For patients initially evaluated in the office setting with suspected ACS, do NOT delay transfer to the ED for troponin testing. 1, 2 Transport urgently to the ED by EMS if clinical evidence of ACS exists. 1 Attempting to obtain troponin in the office delays definitive care and worsens outcomes.

Key Advantage of High-Sensitivity Troponin

High-sensitivity troponin enables more rapid detection or exclusion of myocardial injury and increases diagnostic accuracy compared to conventional assays. 1, 2 The accelerated "rule-out" protocol (1-3 hours vs 3-6 hours) reduces ED length of stay and improves patient flow without compromising safety. 2