Which diagnostic test is considered the gold standard to rule out pulmonary embolism?

• A. Chest x-ray
• B. Spiral CT scan
• C. Ventilation/perfusion scan
• D. Pulmonary angiography

Answer: (D)

Pulmonary angiography directly images the pulmonary arterial vasculature and reveals filling defects caused by an embolus, making it the definitive test to confirm or exclude pulmonary embolism. Because it visualizes the actual clot within the arteries, a negative angiogram effectively rules out PE. Other tests—like chest X-ray, which is non-specific; V/Q perfusion scans, which can be nondiagnostic; and CT pulmonary angiography, which is highly accurate but noninvasive—provide strong support but do not offer the same definitive visualization as angiography. In current practice, CT pulmonary angiography is often used first due to safety and speed, but pulmonary angiography remains the reference standard.