Wells Score Calculator
Deep Vein Thrombosis (DVT) & Pulmonary Embolism (PE)
DVT Clinical Criteria
NICE Guideline Diagnostic Pathways
DVT Unlikely (Score <2) / PE Unlikely (Score ≤4)
- Perform high-sensitivity D-Dimer
- If D-Dimer negative → VTE excluded
- If D-Dimer positive → proceed to ultrasound (DVT) or CTPA (PE)
DVT Likely (Score ≥2) / PE Likely (Score >4)
- Arrange imaging directly
- DVT → Proximal leg vein ultrasound (within 4h if possible)
- PE → CTPA urgently
- Consider interim anticoagulation while awaiting imaging
About the Wells Score
The Wells Score is a validated pre-test probability tool developed by Dr. Philip Wells and colleagues, published originally in 1997 (DVT) and 2000 (PE). It helps clinicians assess how likely a patient is to have a venous thromboembolism (VTE) before diagnostic tests are performed, improving the efficiency and safety of the diagnostic pathway by reducing unnecessary imaging while still identifying high-risk patients.
There are two distinct Wells Scores — one for DVT and one for PE — each with separate criteria and different scoring thresholds. They should not be confused with each other. Both scores stratify patients into "likely" or "unlikely" probability groups, which then determines whether to proceed directly to imaging or to first perform a D-Dimer blood test.
DVT Wells Score — Key Points
The DVT Wells Score consists of nine clinical features that add 1 point each, and one criterion ("alternative diagnosis at least as likely") that subtracts 2 points. This negative criterion is important — it acknowledges that conditions like Baker's cyst, cellulitis, muscle strain, and post-thrombotic syndrome can mimic DVT and should reduce clinical suspicion. A final score ≥2 indicates DVT is "likely"; a score below 2 indicates it is "unlikely."
PE Wells Score — Key Points
The PE Wells Score uses different criteria from the DVT score and different scoring weights. Two major items — clinical signs of DVT (3 points) and PE being the most likely diagnosis (3 points) — carry the highest weight. A score above 4 categorizes PE as "likely" and mandates direct CTPA. A score ≤4 means PE is "unlikely" and D-Dimer testing should precede imaging. The modified Wells PE score (Geneva Score alternative) has also been validated internationally.
D-Dimer in VTE Assessment
D-Dimer is a highly sensitive but non-specific test for VTE. A negative result is very useful for ruling out DVT/PE in low-probability patients. However, D-Dimer is elevated in many other conditions: infection, malignancy, pregnancy, recent surgery, trauma, atrial fibrillation, and simply with advanced age. In high-probability patients or those with elevated D-Dimer, imaging (ultrasound or CTPA) is required to confirm or exclude VTE.
Important Limitations
- The "alternative diagnosis" item requires subjective clinical judgment — inter-rater variability is possible
- Neither score has been well-validated in pregnancy (D-Dimer is normally elevated throughout)
- D-Dimer thresholds may need adjustment for age (age-adjusted D-Dimer: age × 10 mcg/L for patients >50)
- In patients with active malignancy, VTE suspicion should remain high regardless of Wells score
- Negative ultrasound does not exclude calf (distal) DVT — repeat scan in 5–7 days if clinical suspicion remains
Frequently Asked Questions
Is a Wells score of 1 for DVT safe to discharge?
A Wells DVT score below 2 (including a score of 1) indicates DVT is "unlikely." Per NICE guidelines, a negative D-Dimer test in this group effectively rules out DVT and the patient does not require imaging. However, clinical context matters — if clinical suspicion remains high despite a low score or negative D-Dimer, discussion with a senior clinician or haematology is warranted.
Can Wells score be used for recurrent DVT?
The Wells score was originally validated in patients with a first episode of DVT. It can still be used for recurrent VTE assessment, but pre-existing DVT-related findings (post-thrombotic syndrome, residual thrombus) may confound physical examination findings. Previous DVT adds 1 point to the DVT Wells score, acknowledging increased individual risk.
What is the difference between Wells DVT score and Wells PE score?
They use entirely different criteria and different scoring thresholds. The DVT score focuses on local leg findings (swelling, tenderness, collateral veins) with a cutoff at 2 points. The PE score focuses on systemic and respiratory features (tachycardia, immobilization, haemoptysis, malignancy) with a cutoff at 4 points. Using one score for the other condition is inappropriate.