In suspected PE with low probability, which test should be performed first?

In suspected PE with low probability, which test should be performed first?

• A. D-dimer
• B. CT pulmonary angiography
• C. Echocardiography
• D. Chest X-ray

Answer: (A)

When the likelihood of pulmonary embolism is low, start with a D-dimer test. Its high sensitivity means a negative result effectively rules out PE in patients with low pretest probability, sparing them unnecessary imaging. If the D-dimer is positive, you then move on to imaging to confirm the diagnosis, typically CT pulmonary angiography. Chest X-ray isn’t helpful to diagnose PE, and echocardiography can show complications like right heart strain but isn’t diagnostic for PE itself. CT pulmonary angiography is the definitive imaging test used after a positive D-dimer or when clinical suspicion remains high.

When the likelihood of pulmonary embolism is low, start with a D-dimer test. Its high sensitivity means a negative result effectively rules out PE in patients with low pretest probability, sparing them unnecessary imaging. If the D-dimer is positive, you then move on to imaging to confirm the diagnosis, typically CT pulmonary angiography. Chest X-ray isn’t helpful to diagnose PE, and echocardiography can show complications like right heart strain but isn’t diagnostic for PE itself. CT pulmonary angiography is the definitive imaging test used after a positive D-dimer or when clinical suspicion remains high.