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Wells Score for Deep Vein Thrombosis

Estimates the clinical pretest probability of lower-limb deep vein thrombosis to guide D-dimer testing and compression ultrasound.

The Wells score for DVT combines ten clinical variables into a pretest probability for lower-limb deep vein thrombosis. In the widely used two-tier version, "DVT likely" patients proceed to ultrasound and "DVT unlikely" patients are triaged with D-dimer.

🧮 Interactive Calculator

📐 Formula

Sum of criteria (alternative diagnosis −2). ≥ 2 DVT likely; < 2 DVT unlikely.

When to Use

  • Adult patients with a swollen, painful lower limb and suspected DVT.
  • Before ordering D-dimer or compression ultrasound to stratify pretest probability.
  • Outpatient and emergency assessment of possible venous thromboembolism.

How It Works

  • Award +1 for each of nine positive criteria (active cancer, paralysis/immobilisation, bedridden/surgery, deep-vein tenderness, whole-leg swelling, calf swelling > 3 cm, pitting oedema, collateral superficial veins, previous DVT).
  • Subtract 2 if an alternative diagnosis is at least as likely as DVT.
  • Sum the points to obtain the total score.

Interpreting the Result

  • Two-tier: score ≥ 2 = DVT likely; score < 2 = DVT unlikely.
  • DVT unlikely + negative D-dimer: DVT excluded without imaging.
  • DVT likely (or positive D-dimer): proceed to compression ultrasound.
  • Original three-tier: 0 low, 1–2 moderate, ≥ 3 high probability.

Limitations & Pitfalls

  • Less well validated in inpatients, pregnancy and recurrent/known DVT.
  • The subtractive "alternative diagnosis" criterion is clinician-dependent.
  • A single negative ultrasound in a "likely" patient may require repeat imaging.

References

  • Wells PS, Anderson DR, Rodger M, et al. Evaluation of D-dimer in the diagnosis of suspected deep-vein thrombosis. N Engl J Med. 2003;349(13):1227-1235.
  • Wells PS, Hirsh J, Anderson DR, et al. Accuracy of clinical assessment of deep-vein thrombosis. Lancet. 1995;345(8961):1326-1330.

⚕️ For clinical decision support only. Always verify calculations and apply clinical judgment.