Wells Score for DVT (Deep Vein Thrombosis Risk)
Compute the Wells score for deep vein thrombosis (DVT) and read the pretest probability band — used to direct D-dimer and ultrasound work-up.
3-tier: ≤0 Low, 1–2 Moderate, ≥3 High
Low pretest probability
Unlikely + negative high-sensitivity D-dimer rules out DVT.
Refs: Wells PS et al. Lancet 1997;350:1795–1798. Wells PS et al. NEJM 2003;349:1227–1235. Use with D-dimer per local pathway. Clinical decision support tool — confirm against full assessment; not a substitute for clinical judgment.
General calculation reads
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About this tool
The Wells score for DVT (Wells PS et al., Lancet 1997; updated 2003) is a clinical prediction rule that combines nine signs, symptoms, and risk factors to estimate the pretest probability of deep vein thrombosis in a leg. Each item scores +1 except 'an alternative diagnosis as likely or more likely than DVT', which scores −2. The total score categorises the patient as Low (≤0), Moderate (1–2), or High (≥3) pretest probability in the original 3-tier scheme, or Unlikely (≤1) vs Likely (≥2) in the modified 2-tier scheme used in many modern pathways. The score is meant to be used together with D-dimer: an Unlikely score plus a negative high-sensitivity D-dimer effectively rules out DVT without requiring ultrasound; otherwise proceed to compression ultrasound. Reference: Wells PS et al., Lancet 1997;350:1795–1798. Modified rule: Wells PS et al., NEJM 2003;349:1227–1235. Clinical decision support tool — confirm against the full clinical assessment and your local pathway; not a substitute for clinical judgment.
How to use it
- Tick each item that applies (most are +1; the alternative-diagnosis item is −2).
- Read the total score and both the 3-tier and 2-tier risk bands.
- Combine with D-dimer per your local pathway: Unlikely + negative high-sensitivity D-dimer effectively rules out DVT; otherwise proceed to compression ultrasound.
Frequently asked questions
- How is the Wells DVT score actually used?
- Modern pathways are 2-tier: Wells ≥2 = Likely (proceed to ultrasound); Wells ≤1 = Unlikely (do a D-dimer; if negative DVT is essentially ruled out; if positive, ultrasound). Without D-dimer, the 3-tier original is used: Low ≤0, Moderate 1–2, High ≥3.
- Why is one item worth −2?
- "An alternative diagnosis at least as likely as DVT" subtracts 2 because it carries strong negative predictive value — clinicians good at picking up alternative causes (Baker cyst, cellulitis, muscle injury) substantially reduce the prior probability of DVT.
- What counts as recent immobilisation?
- Bedridden for 3 days or more, or recent (within 12 weeks) major surgery requiring regional or general anaesthesia. Both are common after-the-fact discoveries during history-taking.
- Does Wells score apply to upper-limb DVT?
- No — Wells is for lower-limb DVT. For upper-limb DVT there is a separate Constans score.
- What sensitivity does Wells provide?
- Wells alone is a probability estimate, not a diagnostic test. The widely used combination of Wells "Unlikely" plus negative high-sensitivity D-dimer has a sensitivity for DVT in the high 90s percent across multiple validation studies.
- Is data sent anywhere?
- No. Calculation runs in your browser.