Wells Criteria for DVT Calculator
Calculate the Wells Score for Deep Vein Thrombosis (DVT) probability.
A clinical prediction tool to assess pre-test probability of DVT in outpatients.
What Is DVT?
Deep Vein Thrombosis (DVT) is the formation of a blood clot (thrombus) in a deep vein, most commonly in the leg. DVT affects approximately 1–2 people per 1,000 annually. Left untreated, the clot can break free and travel to the lungs, causing a pulmonary embolism (PE) — a potentially life-threatening emergency.
Virchow Triad — Why Clots Form
Three factors promote clot formation (Virchow’s Triad, described by Rudolf Virchow in 1856):
- Venous stasis — slowed blood flow (bed rest, long flights, paralysis)
- Hypercoagulability — increased clotting tendency (cancer, pregnancy, genetic clotting disorders, oral contraceptives)
- Endothelial injury — damage to the vessel wall (surgery, trauma, infection)
The Wells Criteria
Developed by Dr. Philip Wells and colleagues in 1997, the Wells Score is a validated clinical prediction tool. It assigns points based on history, symptoms, and signs to estimate the probability that a patient’s symptoms are caused by DVT. It is widely used in emergency departments and outpatient clinics worldwide.
Scoring and Interpretation
| Score | Probability | Approximate DVT Rate |
|---|---|---|
| 0 or below | Low | ~5% |
| 1 – 2 | Moderate | ~17% |
| 3 or above | High | ~53% |
Clinical Management Implications
Low probability (score ≤ 0): A negative D-dimer test effectively rules out DVT without imaging. D-dimer is a protein fragment released when a blood clot breaks down — elevated D-dimer is sensitive but not specific for DVT.
Moderate probability (score 1–2): D-dimer test first. If elevated, proceed to compression ultrasound. If normal D-dimer, DVT can typically be ruled out.
High probability (score ≥ 3): Proceed directly to compression ultrasound (duplex ultrasonography). Do not use D-dimer alone.
Symptoms to Watch For
Leg pain, swelling, warmth, redness, and tenderness along the path of a deep vein are classic DVT symptoms. However, up to 50% of DVTs are clinically silent. If you experience sudden chest pain, shortness of breath, rapid heart rate, or coughing blood, seek emergency care immediately — these may indicate pulmonary embolism.
This tool is for educational purposes only. Clinical decisions must be made by qualified medical professionals based on the full clinical picture.