What is the Wells Score?

The Wells Score is a clinical prediction rule used to estimate the pre-test probability of deep vein thrombosis (DVT) or pulmonary embolism (PE). It uses clinical features, risk factors, and the clinician's assessment to categorise patients into low, moderate, or high probability groups. This determines which investigations are appropriate — D-dimer for low probability, or imaging (ultrasound for DVT, CTPA for PE) for higher probability.

When should I order a D-dimer?

D-dimer should only be ordered in patients with a LOW pre-test probability (Wells score 0 or less for DVT, 4 or less for PE). A negative D-dimer in a low-probability patient effectively rules out VTE. Do not order D-dimer in high-probability patients — it cannot rule out VTE in this group and a positive result does not help. Proceed directly to imaging.

Wells Score Calculator — DVT & PE Risk Assessment

📋 Source: Wells Score for DVT (Wells et al., 1997) and PE (Wells et al., 2000). Ottawa Hospital Research Institute — Clinical Decision Rules. Validated clinical prediction rules used in Australian emergency and general practice guidelines.
Your doctor or healthcare provider knows your history and circumstances — always follow their personalised advice over general information.

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Wells Score

Clinical prediction rule for DVT and PE. Pre-test probability and investigation pathway.

Clinicians AU Wells 2003 · NICE

Select all that apply

Active cancer

Treatment within 6 months, or palliative care.

Paralysis, paresis, or recent cast

Immobilisation of lower extremity.

Recently bedridden > 3 days or major surgery within 12 weeks

Requiring general or regional anaesthesia.

Localised tenderness along deep venous system

Tenderness over the deep veins of the leg.

Entire leg swollen

Not just calf — entire leg swelling.

Calf swelling > 3cm compared to other leg

Measured 10cm below tibial tuberosity.

Pitting oedema (greater in symptomatic leg)

Confined to the symptomatic leg.

Collateral superficial veins (non-varicose)

Dilated non-varicose superficial veins.

Previously documented DVT

Confirmed prior DVT episode.

Alternative diagnosis at least as likely

Baker's cyst, cellulitis, superficial thrombophlebitis, post-thrombotic syndrome, lymphoedema, muscle strain.

−2

Wells DVT Score

Select all that apply

Clinical signs/symptoms of DVT

Leg swelling, pain on palpation of deep veins.

PE is the most likely diagnosis

Or equally likely — based on clinical judgement.

Heart rate > 100 bpm

Tachycardia at rest.

+1.5

Immobilisation ≥ 3 days or surgery within 4 weeks

Requiring general or regional anaesthesia.

+1.5

Previous DVT or PE

Documented prior VTE episode.

+1.5

Haemoptysis

Coughing up blood.

Active cancer

Treatment within 6 months, or palliative care.

Wells PE Score

Clinical judgement always takes precedence. The Wells Score is a decision support tool — it does not replace clinical assessment. If you are concerned about VTE despite a low score, investigate. Haemodynamically unstable patients with suspected massive PE need emergency management, not scoring.