Wells Score for Deep Vein Thrombosis
Estimate pre-test probability of deep vein thrombosis (DVT). Wells DVT score guides ultrasound and D-dimer decisions in patients with leg swelling or pain.
What is the Wells DVT?
The Wells score for deep vein thrombosis (DVT) is the standard clinical probability assessment tool for patients presenting with a swollen, painful, or red leg. It uses nine readily available clinical features to classify patients as low, moderate, or high probability for DVT, directly guiding whether to proceed to compression duplex ultrasound, D-dimer testing, or both. A negative D-dimer in a low-probability patient safely excludes DVT without imaging. The score is endorsed by NICE, ESC, and the American College of Physicians.
When to use it
Apply to patients presenting with unilateral leg swelling, pain, erythema, or a palpable cord where DVT is a clinical concern. Use before ordering imaging or D-dimer to determine the diagnostic pathway.
Scoring Criteria
Wells DVT — Variables & Points
Active cancer (treatment within 6 months or palliative)
Paralysis, paresis, or recent plaster immobilisation of the leg
Recently bedridden >3 days or major surgery <12 weeks
Localised tenderness along the deep venous system
Entire leg swollen
Calf swelling >3 cm compared to asymptomatic leg
Pitting oedema confined to the symptomatic leg
Collateral superficial veins (non-varicose)
Previously documented DVT
Alternative diagnosis at least as likely as DVT
Subtract 2 points if an alternative diagnosis explains the presentation
Score Interpretation
Low probability
D-dimer first; ultrasound only if D-dimer positive
Moderate probability
D-dimer; if positive → ultrasound
High probability
Ultrasound directly; anticoagulate while awaiting result
Guideline Recommendation
NICE NG158 (2020): Use Wells DVT score to guide the diagnostic pathway for suspected DVT. Low probability + negative D-dimer safely excludes DVT. High probability warrants immediate compression ultrasound.
Clinical Pearls
The negative 2-point "alternative diagnosis" criterion is the most important differentiator — cellulitis, a ruptured Baker's cyst, and superficial thrombophlebitis frequently mimic DVT.
Proximal DVT (popliteal and above) is clinically more important than isolated distal (calf) DVT due to higher embolism risk.
Bilateral leg swelling suggests a systemic cause (heart failure, hypoalbuminaemia, venous insufficiency) rather than DVT.
D-dimer is highly sensitive — a negative result in a low-probability patient has >99% negative predictive value for DVT.
Limitations
Not validated in patients with prior DVT in the same limb — sensitivity is reduced.
Less useful in patients already on anticoagulation.
Does not assess upper extremity DVT.
Interactive Calculator
Interactive calculator requires a free account
Create a free Prognia account to use the Wells DVT calculator — including auto-scored results, interpretation, and CPD logging.
Free plan · No credit card · Instant access
Frequently Asked Questions
What Wells DVT score indicates high probability?
A score of ≥3 indicates high probability of DVT. In these patients, proceed directly to compression duplex ultrasound without waiting for D-dimer results. Some guidelines recommend initiating anticoagulation while imaging is pending if the delay exceeds 4 hours.
Can a negative D-dimer rule out DVT?
Yes — but only in patients with a low or moderate probability Wells DVT score (≤2). In high-probability patients (score ≥3), D-dimer should not be used to exclude DVT, as a negative result does not have sufficient negative predictive value in this population.