Pulmonary Embolism
USMLE/ABIM Question #5
Date Published: 2/15/2025
Vignette:
A 35-year-old woman presents to the emergency department with pleuritic chest pain and mild shortness of breath for 1 day. She takes oral contraceptives but has no other medical history. Vital signs: BP 118/72 mmHg, HR 82/min, RR 16/min, O2 saturation 98% on room air, T 37.1°C. Physical exam is unremarkable with clear lungs and no leg swelling or tenderness. She has no history of VTE, recent surgery, cancer, or hemoptysis.
Wells' Score components:
- Clinical signs/symptoms of DVT: No (0 points)
- PE as likely or more likely than alternative diagnosis: No (0 points)
- Heart rate >100: No (0 points)
- Immobilization/Surgery in previous 4 weeks: No (0 points)
- Previous DVT/PE: No (0 points)
- Hemoptysis: No (0 points)
- Malignancy: No (0 points)
Total Wells' Score: 0 points
Question:
Which of the following is the most appropriate next step in evaluation?
A) Proceed directly to CT pulmonary angiogram
B) Obtain D-dimer testing
C) Start empiric anticoagulation and arrange outpatient follow-up
D) Perform bilateral lower extremity ultrasound
E) Begin workup for alternative diagnoses without PE testing
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Correct Answer:
B) Obtain D-dimer testing
Explanation of Correct Answer:
This patient has:
- Low Wells' score (0 points)
- No high-risk features
- Alternative diagnoses are more likelyD-dimer testing is appropriate because:
- Can safely rule out PE in low-risk patients if negative
- More cost-effective than proceeding directly to imaging
- Avoids unnecessary radiation exposure
- High sensitivity can effectively exclude PE when negative in low-risk patients
Explanation of Incorrect Answers:
A) Direct CTPA - Inappropriate to proceed directly to imaging in low-risk patient without D-dimer; increases cost and radiation exposure unnecessarily.
C) Empiric anticoagulation - Not indicated without confirming diagnosis in stable patient with low pre-test probability.
D) Lower extremity ultrasound - Not the initial test of choice for suspected PE in a patient without DVT symptoms.
E) Skip PE testing - While pre-test probability is low, PE still needs to be properly excluded given the presentation.
Alternative Scenarios:
- If Wells' score was >4 (PE likely), proceed directly to CTPA without D-dimer
- If D-dimer returns elevated, then CTPA would be indicated
- If patient was pregnant, compression ultrasound might be preferred before radiation exposure
Additional Facts:
- D-dimer has >95% sensitivity for PE
- Negative D-dimer in low-risk patient reduces post-test probability to <1%
- Age-adjusted D-dimer cutoff (age × 10 µg/L) can be used in patients >50 years
- PERC rule can be used in very low-risk patients
- CT imaging exposes patient to approximately 7 mSv radiation
Main Takeaway:
In patients with low Wells' score (<2 points), D-dimer testing should be performed before proceeding to CT pulmonary angiogram to safely exclude PE while minimizing unnecessary testing.
