| Points | Criterion | Category | Clinical Definition |
|---|---|---|---|
| ◆ +1 Point Each — Active Conditions & Physical Signs | |||
+1 |
Active CancerCURRENT OR RECENT TREATMENT | Oncological | Treatment within past 6 months, or currently receiving palliative care; includes solid tumours and haematological malignancies |
+1 |
Paralysis / ParesisLOWER LIMB IMMOBILISATION | Neurological | Paralysis, paresis or recent plaster immobilisation of the lower extremities; any cause reducing calf-muscle pump function |
+1 |
Bedridden > 3 Days / SurgeryRECENT IMMOBILISATION | Surgical / Immobility | Recently bedridden for ≥3 days OR major surgery within 12 weeks requiring general or regional anaesthesia |
+1 |
Localised TendernessDEEP VENOUS SYSTEM | Physical Sign | Localised tenderness along the distribution of the deep venous system; palpation along posterior calf, popliteal fossa or medial thigh |
+1 |
Entire Leg SwollenWHOLE LIMB OEDEMA | Physical Sign | Entire leg is swollen; unilateral swelling extending above the knee; not limited to calf or ankle |
+1 |
Calf Swelling > 3 cmASYMMETRIC CALF | Measurement | Calf swelling >3cm compared to asymptomatic leg; measured 10cm below tibial tuberosity; unilateral asymmetry |
+1 |
Pitting OedemaSYMPTOMATIC LEG ONLY | Physical Sign | Pitting oedema confined to the symptomatic leg; unilateral pitting differentiates from bilateral oedema of cardiac or hepatic origin |
+1 |
Collateral Superficial VeinsNON-VARICOSE | Physical Sign | Collateral superficial veins (non-varicose); dilated superficial veins acting as collateral channels due to deep venous obstruction |
+1 |
Previous DVTDOCUMENTED HISTORY | History | Previously documented deep vein thrombosis; confirmed by objective testing (duplex ultrasound or venography) in prior episodes |
| ◆ −2 Points — Alternative Diagnosis Considered | |||
−2 |
Alternative DiagnosisAS OR MORE LIKELY THAN DVT | Differential | Alternative diagnosis at least as likely as DVT; e.g., cellulitis, muscle tear, Baker's cyst, superficial thrombophlebitis, post-operative swelling, lymphoedema |
| Score | Probability Band | DVT Prevalence | Interpretation & Notes |
|---|---|---|---|
≤ 0 |
Low
|
~5% | Low pre-test probability; DVT unlikely in majority of patients. If D-dimer negative → DVT excluded without imaging. D-dimer positive → proceed to ultrasound. |
1 – 2 |
Moderate
|
~17% | Moderate pre-test probability; significant proportion have DVT. D-dimer testing recommended; if elevated or unavailable → duplex ultrasound mandatory. |
≥ 3 |
High
|
~53% | High pre-test probability; majority of patients have DVT. Proceed directly to duplex ultrasound — do NOT rely on D-dimer alone to exclude diagnosis at this threshold. |
| ◆ Revised Two-Level / Two-Tier Classification (NICE / SIGN Guideline Adaptation) | |||
≤ 1 |
DVT Unlikely
|
< 17% | Two-tier: DVT unlikely. Perform D-dimer; if negative → no further investigation needed. If positive → proximal leg ultrasound within 4 hours or anticoagulate pending scan. |
≥ 2 |
DVT Likely
|
≥ 17% | Two-tier: DVT likely. Arrange proximal leg ultrasound within 4 hours. If unavailable → perform D-dimer & give interim anticoagulation; repeat ultrasound within 24 hours. |
| Score | Risk Tier | First-Line Investigation | Clinical Management Steps |
|---|---|---|---|
≤ 0 |
Low Risk | D-dimer (high-sensitivity) | D-dimer negative → DVT excluded; no anticoagulation. D-dimer positive → proximal duplex ultrasound. Negative ultrasound with low Wells → DVT excluded; no further action. |
1 – 2 |
Moderate Risk | D-dimer + Duplex Ultrasound | D-dimer and duplex ultrasound in parallel or sequentially. Positive ultrasound → initiate anticoagulation (LMWH or DOAC). Negative ultrasound + negative D-dimer → DVT excluded. |
≥ 3 |
High Risk | Proximal Duplex Ultrasound | Proceed directly to duplex ultrasound; do not delay for D-dimer. Consider empirical anticoagulation while awaiting imaging. Positive → confirm DVT; treat. Negative → repeat in 7 days if clinical suspicion persists. |
Repeat –ve |
Persistent Suspicion | Serial Ultrasound / CT Venography | Initial negative ultrasound with high Wells → repeat duplex at 5–7 days OR consider CT venography / MR venography to evaluate iliac/pelvic veins not accessible to standard ultrasound. |
| Type | Point | Details |
|---|---|---|
| Pearl | Bilateral DVT | Wells score is designed for unilateral symptomatic leg. Bilateral swelling more likely suggests systemic causes (cardiac failure, hypoalbuminaemia, pelvic mass). Apply score to each leg independently if bilateral symptoms. |
| Pearl | Pregnancy | Wells score has not been validated in pregnancy. D-dimer is physiologically elevated in pregnancy. Duplex ultrasound is the primary investigation; if negative with ongoing suspicion, MR venography is preferred over CT. |
| Caution | On Anticoagulation | Wells score is less reliable in patients already receiving therapeutic anticoagulation for other indications. Perform imaging regardless of score if extending anticoagulation duration is being considered. |
| Caution | Recurrent DVT | Diagnosing recurrent ipsilateral DVT with duplex ultrasound is challenging due to residual thrombus. Comparison with prior ultrasound reports is essential. D-dimer remains useful as a negative predictor even in recurrence. |
| Limitation | Does Not Assess Pelvic Veins | Standard duplex ultrasound and Wells score do not adequately assess iliofemoral and pelvic venous segments. Isolated iliac DVT may present with a low Wells score. CT/MR venography required when pelvic DVT is clinically suspected. |
| Limitation | Subjective Criterion | The "alternative diagnosis as likely" criterion introduces clinician subjectivity. Inter-observer variability has been documented. Score performs best when applied by experienced clinicians with systematic examination. Consider structured documentation. |