Which imaging test is described as the most reliable for diagnosing a pulmonary embolism?

• A. Spiral CT
• B. V/Q Scan
• C. ABG
• D. D-Dimer

Answer: (A)

The main idea is that the best imaging test to confirm a pulmonary embolism is CT pulmonary angiography with spiral acquisition. This test directly visualizes the pulmonary arteries and can reveal filling defects caused by emboli, giving a clear, definitive diagnosis in many cases. It combines high accuracy with speed and broad availability, and it can also show other possible causes of symptoms in the same study.

V/Q scanning is more limited because results can be nondiagnostic or ambiguous, especially in patients with preexisting lung disease or an abnormal chest X-ray, making it less reliable for a definitive diagnosis. Arterial blood gas isn’t diagnostic for PE; it may show hypoxemia or abnormal acid-base status but cannot confirm an embolus. D-Dimer is a screening tool with high sensitivity but poor specificity; a negative result can help rule out PE in low-risk patients, but a positive result requires imaging to confirm, so it isn’t a definitive diagnosis by itself.

So, CT pulmonary angiography (spiral CT) is considered the most reliable method for diagnosing pulmonary embolism.