What is the Wells score for DVT?

The Wells DVT score is a validated clinical prediction rule that combines nine clinical features into a single number to estimate the pre-test probability of deep vein thrombosis. It helps decide whether a patient needs a D-dimer test, a compression ultrasound, or both.

How is the Wells DVT score interpreted?

In the three-tier model, a score of 0 or less is low probability, 1 to 2 is moderate, and 3 or more is high. In the more common two-tier model, a score of 2 or more is DVT likely and below 2 is DVT unlikely, which then guides D-dimer and ultrasound pathways.

Why does an alternative diagnosis subtract points?

If a condition at least as likely as DVT can explain the leg symptoms, such as cellulitis or a ruptured Baker's cyst, the probability of DVT falls. The Wells rule reflects this by subtracting two points, which can move a patient into a lower-risk pathway.

What do I do with a DVT-unlikely result?

For a DVT-unlikely score, a negative high-sensitivity D-dimer can safely rule out DVT without imaging. A positive D-dimer or a DVT-likely score should be followed by a proximal leg compression ultrasound, per NICE and other guidelines.

Does the Wells DVT score replace imaging?

No. The score only estimates probability and directs the testing pathway. A definitive diagnosis of DVT still relies on compression ultrasound. The tool supports clinical judgement and local protocols rather than replacing them.

What is the Wells Score for DVT?

Calculate the Wells DVT score from clinical features such as active cancer, immobilisation, calf swelling, tenderness, and alternative diagnosis to stratify low, moderate, or high pre-test probability and guide D-dimer and ultrasound decisions. It runs free in your browser on Gera Tools, with nothing uploaded.

Wells Score for DVT — Gera Tools

Name: Wells Score for DVT
Creator: Gera Tools
License: https://creativecommons.org/licenses/by/4.0/

What the Wells DVT score does

The Wells score for deep vein thrombosis is a clinical prediction rule that turns bedside findings into an estimated pre-test probability of DVT. By stratifying patients before any blood test or scan, it allows clinicians to use D-dimer testing and compression ultrasound efficiently and safely, avoiding unnecessary imaging in low-risk patients while ensuring high-risk patients are investigated promptly.

Scoring each criterion

Each of the following clinical features scores +1:

Criterion	Notes on assessment
Active cancer	On treatment within 6 months, or palliative
Paralysis, paresis, or recent plaster immobilisation	Applies to the lower limb
Recently bedridden ≥3 days, or major surgery within 12 weeks requiring anaesthesia	Either criterion qualifies
Localised tenderness along the deep venous system	Femoral and/or popliteal
Entire leg swollen	Not just the calf
Calf swelling >3 cm compared to asymptomatic leg	Measured 10 cm below the tibial tuberosity
Pitting oedema confined to symptomatic leg	Not bilateral
Collateral superficial (non-varicose) veins	Present on examination
Previously documented DVT	Objectively confirmed

One feature scores −2:

Criterion	Notes
Alternative diagnosis at least as likely as DVT	For example: cellulitis, ruptured Baker’s cyst, muscle tear, superficial thrombophlebitis

Interpreting the total score

In the two-tier model (more commonly used in UK/NICE guidance):

Score	Risk tier	Suggested pathway
`< 2`	DVT unlikely	Perform high-sensitivity D-dimer; if negative, DVT excluded
`≥ 2`	DVT likely	Proximal leg compression ultrasound regardless of D-dimer

In the three-tier model:

Score	Risk tier	Approximate DVT prevalence
`≤ 0`	Low	Roughly 5%
`1–2`	Moderate	Roughly 17%
`≥ 3`	High	Roughly 53%

Worked example

A 68-year-old patient attends with a unilateral swollen right leg. On assessment: active cancer (treated 3 months ago, +1), entire leg swollen (+1), calf swelling of 4 cm vs the left leg (+1), pitting oedema in the right leg only (+1), and no alternative diagnosis as likely as DVT. Total score = 4.

This is DVT likely (two-tier) and high probability (three-tier). The appropriate next step is proximal leg compression ultrasound — a D-dimer result would not safely exclude DVT at this score and is not needed before imaging.

Now consider a 35-year-old with a mildly swollen right calf who has just returned from a long-haul flight. Examination finds only localised calf tenderness (+1), but the clinician considers cellulitis an equally likely diagnosis (−2). Total = −1 — DVT unlikely. A high-sensitivity D-dimer, if negative, can safely rule out DVT without ultrasound.

Important clinical context

The Wells DVT score is validated for outpatient assessment of suspected lower-limb DVT. It is not designed for:

Upper-extremity DVT (separate criteria apply)
Patients already on anticoagulation
Recurrent DVT in the same limb (prior DVT has already been awarded +1, which may skew the score)
Pregnant patients (higher baseline DVT risk requires adjusted assessment)

Always use the score alongside clinical judgement and your local DVT pathway. In the UK, NICE NG158 recommends the two-tier Wells score combined with whole-leg ultrasound in the DVT-likely group. In North America and elsewhere, local guidelines may differ. This tool supports — but does not replace — clinical decision-making.