In suspected acute pulmonary embolism, which diagnostic test is most appropriate to confirm the diagnosis?

• A. D-dimer
• B. Chest X-ray
• C. Computed tomography angiogram of the chest
• D. Ventilation-perfusion scan

Answer: (C)

The main idea is that confirming acute pulmonary embolism requires imaging that directly shows a clot in the pulmonary arteries. Computed tomography angiography of the chest does exactly this by visualizing the pulmonary arteries and revealing a filling defect caused by a thrombus. It offers rapid, highly accurate confirmation and also allows assessment for alternative causes of symptoms, which is crucial in acute settings.

D-dimer, while highly sensitive, is not specific enough to confirm PE. A negative D-dimer can help rule out PE in patients with low pretest probability, but a positive result does not establish the diagnosis on its own. Chest X-ray is not diagnostic for PE; it often appears normal or shows nonspecific findings and cannot confirm emboli. A ventilation-perfusion scan can be useful if CTA is not feasible (for example, due to contrast allergy or kidney issues, or in pregnancy), but it frequently yields nondiagnostic or indeterminate results and is less direct than CTA in identifying an actual clot.

Therefore, when the goal is definitive confirmation in suspected acute PE, CT pulmonary angiography is the best choice.