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

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Question:

Which of the following is the most appropriate next step in evaluation?

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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

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:

1. If Wells' score was >4 (PE likely), proceed directly to CTPA without D-dimer
2. If D-dimer returns elevated, then CTPA would be indicated
3. 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.