Wells score for DVT
Two-level Wells score for deep vein thrombosis.
What the Wells DVT score is for
It estimates the pre-test probability of a deep vein thrombosis in a patient with a painful or swollen leg, and tells you whether to scan straight away or start with a D-dimer. NICE NG158 uses the two-level version.
The criteria
One point each for: active cancer; paralysis, paresis or recent plaster cast on the leg; bedridden for 3 days or more, or major surgery within 12 weeks; localised tenderness along the deep veins; entire leg swollen; calf swelling at least 3 cm more than the other side; pitting oedema confined to the symptomatic leg; collateral superficial (non-varicose) veins; previous DVT. Subtract 2 if another diagnosis is at least as likely as DVT.
Measure both calves 10 cm below the tibial tuberosity with a tape.
Interpreting the score
- 2 or more: DVT likely. Proximal leg ultrasound within 4 hours. If that is not possible, do a D-dimer, start interim anticoagulation and scan within 24 hours. If the scan is negative but the D-dimer is positive, repeat the scan 6–8 days later.
- 1 or less: DVT unlikely. D-dimer. If positive, ultrasound as above; if negative, DVT is unlikely and you should look for another cause.
Worked example
A 55-year-old on chemotherapy has a swollen left calf, 4 cm bigger than the right, with pitting oedema. Points: cancer 1, calf difference 1, pitting oedema 1 = 3. DVT likely: request an urgent Doppler ultrasound and start anticoagulation if the scan will be delayed.
Limitations and pitfalls
- The "alternative diagnosis" item is where most scoring errors happen. Common alternatives are cellulitis, a ruptured Baker's cyst, muscle injury, superficial thrombophlebitis and bilateral oedema from heart, liver or kidney disease.
- D-dimer is raised after surgery, in pregnancy, infection, cancer and older age, so a positive result means "scan", not "DVT".
- The score is not validated in pregnancy; involve a senior and scan.
- Check platelets, kidney function and bleeding risk before choosing an anticoagulant.
See calf pain and DVT, cellulitis, Wells score for PE, enoxaparin, rivaroxaban and the textbook chapter on DVT and pulmonary embolism.
Frequently asked questions
What Wells score means DVT is likely?
2 points or more on the two-level Wells score. A score of 1 or less means DVT is unlikely and a D-dimer is the next step.
Where do I measure calf circumference?
10 cm below the tibial tuberosity on both legs. A difference of 3 cm or more scores a point.
Can a negative D-dimer rule out DVT?
Only when the Wells score shows DVT is unlikely. If DVT is likely, an ultrasound is needed whatever the D-dimer result.
Should I start anticoagulation before the scan?
If DVT is likely and the ultrasound cannot be done within 4 hours, NICE advises interim anticoagulation, provided there is no contraindication, with the scan within 24 hours.
A calculator supports, but does not replace, clinical judgement. Check results before acting on them.