About the Wells Score for DVT
The Wells score for deep vein thrombosis (DVT) estimates how likely a leg DVT is before imaging. It was developed by Philip Wells and colleagues in Ottawa (Lancet 1997) and updated in 2003 (NEJM) to include a previously documented DVT. Nine clinical features score +1 each, and the judgement that an alternative diagnosis is at least as likely as DVT scores −2, giving a range from −2 to 9.
The modified score is usually used in two tiers: DVT likely (2 or more) or DVT unlikely (1 or less). In the 2003 NEJM trial, DVT was safely ruled out in patients judged unlikely who also had a negative D-dimer, avoiding ultrasound in 39% of the D-dimer group. The calculator also shows the classic three-tier grouping, with the pooled DVT prevalence from a 2006 JAMA meta-analysis of more than 8,000 outpatients: about 5% low, 17% moderate and 53% high.
The rule was derived and validated in outpatients with suspected lower-limb DVT. It is less reliable in hospital inpatients, pregnancy and upper-limb DVT, and it guides testing — it does not diagnose or exclude DVT on its own.
With the default inputs, the wells dvt score is 2. Change any value above to recalculate instantly.
How to use the wells score for dvt
- 1Use this for an outpatient with a suspected DVT of the leg.
- 2Tick each risk factor and examination finding that is present.
- 3Tick "alternative diagnosis" if something else (e.g. cellulitis, Baker’s cyst) is at least as likely.
- 4Read the two-tier result (likely/unlikely) and three-tier probability.
- 5Use it to choose between D-dimer and ultrasound, following local pathways.
Formula and method
Nine features each add one point: active cancer, paralysis/paresis or recent cast, bedridden more than 3 days or major surgery within 12 weeks, localised deep-vein tenderness, whole-leg swelling, calf swelling more than 3 cm compared with the other leg, pitting oedema in the symptomatic leg, collateral superficial veins, and a previously documented DVT (added in the 2003 modification). Two points are subtracted if another diagnosis is at least as likely.
Two-tier interpretation (Wells 2003): ≥ 2 DVT likely, ≤ 1 DVT unlikely. Three-tier interpretation (Wells 1997): ≤ 0 low, 1–2 moderate, ≥ 3 high. The pooled prevalences shown (5%, 17%, 53%) come from the 2006 JAMA rational clinical examination meta-analysis of 14 studies.
- DVT
- Deep vein thrombosis
Worked examples
Tender, swollen calf after a long illness
Deep-vein tenderness (+1) and calf swelling over 3 cm (+1) give 2 points: DVT likely on the two-tier rule, moderate probability (about 17%) on the three-tier rule.
Likely cellulitis
Calf swelling (+1) with an alternative diagnosis at least as likely (−2) gives −1: DVT unlikely and low probability (about 5%). A D-dimer would usually be the next test.
Cancer patient after surgery
Active cancer, recent major surgery, whole-leg swelling, pitting oedema, tenderness and calf swelling total 6 points — high probability, with a pooled prevalence of about 53%.
Frequently asked questions
What Wells score means DVT is likely?+
On the modified two-tier Wells rule, a score of 2 or more means DVT is likely and a score of 1 or less means DVT is unlikely. Most current guidelines, including NICE NG158, use this version.
Can a negative D-dimer rule out DVT?+
In patients with an unlikely Wells score (≤ 1), a negative D-dimer makes DVT very unlikely and ultrasound can usually be omitted, as shown in the 2003 NEJM trial. In patients with a likely score, imaging is still required.
Why is there a minus 2 for an alternative diagnosis?+
If another condition such as cellulitis, a ruptured Baker’s cyst, muscle injury or superficial thrombophlebitis explains the symptoms at least as well, the probability of DVT is substantially lower, so two points are subtracted.
Does the Wells score work for inpatients?+
It was derived in outpatients. Studies in hospitalised patients show poorer accuracy because many inpatients have several risk factors, so imaging thresholds are often lower in that setting.
What is the difference between the original and modified Wells DVT scores?+
The 2003 modified score adds one point for a previously documented DVT and is interpreted in two tiers (likely ≥ 2, unlikely ≤ 1). The 1997 original used three tiers: low, moderate and high.
For healthcare professionals and education only. This calculator implements a published formula or score but is not a diagnosis and does not replace clinical judgment. Verify inputs and results against the original source before using them in patient care.