DVT and Pulmonary Embolism: Wells Score, Diagnosis, and Anticoagulation
VTE diagnosis is one of the highest-stakes clinical decisions in medicine — and one of the most systematically testable. Boards reward students who know the Wells score and can walk through the diagnostic algorithm without hesitation.
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Updated July 2026
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The 60-second version
Wells PE score ≤4: D-dimer first; >4: go directly to CTA
Negative D-dimer in low-pretest-probability = PE excluded
Massive PE (SBP <90): systemic tPA if no contraindications
DOACs (rivaroxaban, apixaban) are first-line for VTE anticoagulation
Cancer-associated VTE: LMWH or rivaroxaban preferred over warfarin
Clinical signs of DVT: 3 pts. PE more likely than alternate diagnosis: 3 pts. HR >100: 1.5 pts. Immobilization ≥3 days or surgery within 4 weeks: 1.5 pts. Prior DVT/PE: 1.5 pts. Hemoptysis: 1 pt. Malignancy on treatment: 1 pt. Score ≤4 = PE unlikely → D-dimer. Score >4 = PE likely → CTA pulmonary angiography directly.
D-dimer: What It Can and Cannot Do
D-dimer is a sensitive but non-specific test. Negative D-dimer in a low-pretest-probability patient effectively rules out PE — no further imaging needed. Positive D-dimer requires imaging (CTA) to confirm. D-dimer is USELESS in high-pretest-probability patients — go directly to CTA. Also elevated in: pregnancy, malignancy, recent surgery, sepsis, advanced age (falsely positive >90% of patients over 80).
Massive vs Submassive PE
Massive PE: hemodynamic instability (SBP <90 or drop >40 mmHg for >15 min). Treatment: systemic thrombolysis (tPA) if no contraindications, or catheter-directed therapy/surgical embolectomy. Submassive PE: normotensive but with RV dysfunction (Echo/CT) or troponin/BNP elevation. Anticoagulate; consider thrombolytics on case-by-case basis. Low-risk PE: normotensive, no RV strain, consider outpatient treatment (PESI score).
Anticoagulation Options
First-line: LMWH (enoxaparin) bridge to warfarin, or direct oral anticoagulants (DOACs) — rivaroxaban or apixaban preferred (no bridging needed, oral, fixed dosing). Duration: provoked PE (surgery/immobility) = 3 months. Unprovoked PE = minimum 3 months, consider indefinite. Cancer-associated VTE: LMWH or rivaroxaban preferred over warfarin (INR variability in cancer). Contraindications to anticoagulation → IVC filter.
Test yourself
Quick check — 3 questions
1. A 55-year-old post-op patient (knee replacement 2 weeks ago) presents with pleuritic chest pain and dyspnea. HR 108, O2 sat 94%. No clinical DVT signs. Wells PE score (excluding DVT signs)? Is CTA or D-dimer next?
Explanation. PE more likely than alternative (3) + HR >100 (1.5) + surgery within 4 weeks (1.5) = 6 total. Score >4 = PE likely → go directly to CTA pulmonary angiography. D-dimer is not useful in high-pretest-probability patients.
2. A patient with confirmed PE has BP 78/50 not responding to IV fluids. Which intervention is indicated?
Explanation. Massive PE (SBP <90 mmHg with hemodynamic instability) is the indication for systemic thrombolysis (tPA) in the absence of contraindications. This is a true emergency — thrombolytics restore pulmonary perfusion and RV function. Anticoagulation alone is insufficient for hemodynamically unstable PE.
3. A 30-year-old woman with first unprovoked PE is started on rivaroxaban. Duration of anticoagulation?
Explanation. Unprovoked PE: minimum 3 months of anticoagulation, then weigh recurrence risk vs. bleeding risk for indefinite therapy decision. Guidelines recommend considering indefinite anticoagulation for most patients with unprovoked PE, but this requires shared decision-making accounting for patient preferences and bleeding risk.
Frequently asked questions
When should you order a V/Q scan instead of CTA for PE?
V/Q scan is preferred over CTA in: pregnancy (significantly less radiation to the fetus, though both involve some exposure), contrast allergy, severe renal insufficiency (contrast nephropathy risk), and patients with significantly abnormal chest X-ray (low V/Q specificity). A normal V/Q essentially excludes PE; high-probability V/Q has >80% PPV.
What is the appropriate D-dimer threshold for older patients?
Age-adjusted D-dimer threshold = patient age × 10 µg/L (for patients >50 years). Using the standard threshold of 500 µg/L in elderly patients leads to very high false-positive rates. The age-adjusted threshold improves specificity without meaningfully sacrificing sensitivity, reducing unnecessary CTA in older low-pretest-probability patients.
Which patients with PE can be treated as outpatients?
Low-risk PE patients (PESI class I-II or sPESI 0) with no contraindications, reliable home monitoring access, and ability to take oral anticoagulation can be discharged with DOAC therapy. Key criteria: normotensive, no significant hypoxia, no RV dysfunction, no significant bleeding risk, no severe comorbidities. Always ensure close 48–72 hour follow-up.
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