What initial laboratory tests should be obtained for a patient presenting to the hospital with chest pain?

Initial Laboratory Tests for Hospitalized Chest Pain

Obtain a high-sensitivity cardiac troponin immediately upon presentation and a 12-lead ECG within 10 minutes—these two tests form the cornerstone of your initial laboratory and diagnostic workup. 1, 2

Mandatory Immediate Laboratory Tests

Cardiac Biomarkers

• High-sensitivity cardiac troponin (hs-cTn) is the single most important laboratory test; draw it immediately on arrival because it is the most sensitive and specific biomarker for myocardial injury, outperforming CK and CK-MB. 1, 2
• Repeat hs-cTn at 1–3 hours after the initial draw (or conventional troponin at 3–6 hours if high-sensitivity assays are unavailable) because a single normal result does not exclude acute coronary syndrome. 1, 2
• If troponin is unavailable, measure CK-MB mass on admission and repeat at 10–12 hours after symptom onset, though troponins are strongly preferred for their superior cardiac specificity. 3, 2

Complete Blood Count and Basic Metabolic Panel

• Hemoglobin, red blood cell count, white blood cell count, and platelet count should be obtained to assess for anemia (which can precipitate or worsen ischemia), infection, and baseline hematologic status before potential antiplatelet or anticoagulation therapy. 3
• Creatinine measurement is essential to assess renal function before administering contrast agents for imaging or adjusting medication dosing. 3

Inflammatory Markers

• C-reactive protein (CRP) can be measured as part of the initial workup, particularly when considering inflammatory causes such as pericarditis or myocarditis. 3

Additional Laboratory Tests Based on Clinical Context

When Pulmonary Embolism Is Suspected

• Age- and sex-adjusted D-dimer should be obtained in patients with low-to-intermediate probability of pulmonary embolism; a negative result effectively rules out PE. 1
• Proceed directly to CT pulmonary angiography without D-dimer testing when clinical probability is high (sudden dyspnea, pleuritic pain, tachycardia >90% of PE cases). 1

When Aortic Dissection Is Suspected

• Do not delay imaging for laboratory results when dissection is suspected (sudden "ripping" pain, pulse differential, blood pressure difference >20 mmHg between arms); withhold aspirin and heparin and arrange immediate CT angiography, MRI, or transesophageal echocardiography. 1, 2

Arterial Blood Gas

• Arterial blood gas determination should be obtained in patients with respiratory distress, suspected pulmonary embolism, or hemodynamic instability to assess oxygenation and acid-base status. 3

Critical Timing and Serial Testing

• 30–40% of acute myocardial infarctions present with a normal or nondiagnostic initial ECG, so normal initial tests do not exclude ACS. 1, 2
• Serial ECGs every 15–30 minutes should accompany serial troponin testing when clinical suspicion remains high despite initial normal results. 1, 2
• A single-sample rule-out strategy is acceptable only for patients whose chest pain onset occurred ≥3 hours before presentation, who have a normal ECG, and whose high-sensitivity troponin level is below the assay's limit of detection. 1

Sex-Specific Considerations

• Use sex-specific hs-cTn thresholds (>16 ng/L for women vs >34 ng/L for men) because universal cut-offs miss approximately 30% of women with STEMI. 1
• Women more frequently present with accompanying symptoms (jaw/neck pain, nausea, fatigue, dyspnea, epigastric discomfort) rather than classic chest pressure, yet troponin testing remains equally essential. 1

Common Pitfalls to Avoid

• Do not delay emergency department transfer for troponin results in office or outpatient settings when ACS is suspected; immediate EMS transport takes priority over laboratory testing. 1, 2
• Do not rely on a single normal troponin to exclude myocardial infarction; serial testing is mandatory. 1, 2
• Do not use nitroglycerin response as a diagnostic criterion because esophageal spasm and other non-cardiac conditions may also respond. 1

High-Risk Features Requiring Immediate CCU Admission

• Troponin above the 99th percentile, ongoing rest pain >20 minutes with ischemic ECG changes, hemodynamic instability (SBP <100 mmHg, HR >100 or <50 bpm), or evidence of left-ventricular failure (crackles, S3 gallop, new murmurs) mandate immediate coronary care unit admission regardless of other laboratory values. 1, 2