American Board of Internal Medicine (ABIM) Certification Practice Exam

What is the preferred initial diagnostic test for pulmonary embolism in a pregnant patient?

1. CT pulmonary angiography

2. Ventilation-perfusion (V/Q) lung scan

3. Lower extremity venous duplex ultrasonography

4. D-dimer testing

The correct answer is: Lower extremity venous duplex ultrasonography

In the context of diagnosing pulmonary embolism (PE) in a pregnant patient, lower extremity venous duplex ultrasonography is considered the preferred initial diagnostic test. The rationale for this choice stems from both the safety profile and the effectiveness of venous duplex ultrasound in detecting deep vein thrombosis (DVT), which is a common source of pulmonary emboli. Pregnant patients have an increased risk of venous thromboembolism due to physiological changes, including increased clotting factors and changes in venous return. Therefore, the presence of DVT becomes a significant concern when assessing potential PE. The use of lower extremity venous duplex ultrasonography allows for the non-invasive and safe examination of the veins in the legs, helping to identify thrombosis without exposing the patient or fetus to radiation. While other diagnostic tests, such as CT pulmonary angiography and V/Q lung scans, can effectively diagnose PE, they involve exposure to radiation. This exposure can pose risks during pregnancy, thereby making these options less favorable as initial tests. D-dimer testing has limitations in pregnant patients because D-dimer levels can be elevated due to normal physiological changes during pregnancy, leading to false positives and unnecessary further testing. Ultimately, focusing on the safe detection of DVT