Medical AIWells criteria for deep vein thrombosis
A clinical prediction rule that places a patient with suspected deep vein thrombosis into a pretest-probability category. The modern two-level version (DVT likely vs unlikely) is paired with D-dimer: an unlikely score plus a negative D-dimer can safely defer or avoid ultrasound. It is a triage tool, not a stand-alone rule-out.
How to measure each input
- Calf swelling
- Measure the calf circumference 10 cm below the tibial tuberosity on both legs. A difference of more than 3 cm on the symptomatic side scores the point.
- Active cancer
- Counts if cancer treatment is ongoing, was within the previous 6 months, or is palliative.
- Recent immobilisation or surgery
- Score for recent plaster immobilisation or paralysis of the leg, being bedridden for at least 3 days, or major surgery within 12 weeks under general or regional anaesthesia.
- Alternative diagnosis
- If a diagnosis other than DVT (cellulitis, ruptured Baker cyst, superficial thrombophlebitis, muscle injury, post-thrombotic syndrome) is at least as likely, subtract 2 points.
Interpretation
| Band | Meaning |
|---|---|
| < 2, DVT unlikely | Two-tier: DVT unlikely. Combined with a negative high-sensitivity D-dimer, this safely defers or avoids compression ultrasound. A positive D-dimer should prompt ultrasound. (In the original three-tier model, <= 0 is low and 1 to 2 is moderate probability.) |
| >= 2, DVT likely | Two-tier: DVT likely. Proceed to compression ultrasound. Do not rely on D-dimer alone to exclude DVT in this group. (In the original three-tier model, a score of 3 or more is high probability.) |
Pitfalls, exclusions and caveats
- The Wells DVT rule and the Wells PE rule are different scores with different items. Do not interchange them.
- It is not validated as a stand-alone rule-out. The safe pathway pairs a 'DVT unlikely' score with a negative high-sensitivity D-dimer; a positive D-dimer or a 'likely' score requires ultrasound.
- D-dimer loses specificity in pregnancy, malignancy, recent surgery, and older age, so the unlikely-plus-negative-D-dimer pathway is less useful in those groups.
- The -2 alternative-diagnosis item is subjective and is the main source of inter-rater variation; weigh it carefully.
- Performance is best in symptomatic outpatients with a first suspected DVT. It is less well validated in inpatients and recurrent disease.
1 point each: active cancer + paralysis, paresis, or recent plaster immobilisation of a leg + recently bedridden >= 3 days or major surgery within 12 weeks + localised tenderness along the deep venous system + entire leg swollen + calf swelling > 3 cm vs the asymptomatic side + pitting oedema confined to the symptomatic leg + collateral superficial (non-varicose) veins + previously documented DVT. MINUS 2 if an alternative diagnosis is at least as likely as DVT.The Wells DVT criteria were described by Wells et al. (1997, 1997 original; 2003 two-level model). This implementation is an educational tool and is not affiliated with the original authors.
Frequently asked
How is the Wells DVT score different from the Wells PE score?
They share an author and the general approach but have entirely different items and cutoffs. The DVT score uses leg findings (swelling, tenderness, calf measurement) for suspected deep vein thrombosis; the PE score uses items like haemoptysis and tachycardia for suspected pulmonary embolism. Use the one that matches the suspected diagnosis.
Can I rule out DVT with the Wells score alone?
No. A 'DVT unlikely' score (less than 2) must be combined with a negative high-sensitivity D-dimer to safely defer or avoid ultrasound. A 'likely' score or a positive D-dimer requires compression ultrasound.
Why can the score be negative?
The item for an alternative diagnosis being at least as likely subtracts 2 points, so a patient with no positive features and a plausible alternative diagnosis can score as low as -2. Any total below 2 falls in the 'DVT unlikely' band.
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