Estimates the pre-test probability of pulmonary embolism to decide between a D-dimer and CT pulmonary angiography.
Result
Answer the seven questions to see the score.
0 of 7 items scored
Sources
3 studies
3
studies
1,457
citations
449
PubMed papers
Evidence
Known limitations
In 3,306 patients, the two-tier Wells score classified 66.7% as “PE unlikely”. Of those with a normal D-dimer who were left untreated, 0.5% had a venous thromboembolism in 3 months; among all patients whose CT excluded pulmonary embolism, 1.3% did.
Across 29 studies with 31,215 patients, pooled prevalence was 6%, 23% and 49% for low, intermediate and high Wells probability, and 8% and 34% for “PE unlikely” and “PE likely”. The Wells and Geneva scores had similar accuracy but are not interchangeable.
J Thromb Haemost: Journal Metrics Score 3.5, Q1 · cited 342 times
Derived the eight-item PERC rule to identify emergency patients at very low probability of pulmonary embolism in whom even a D-dimer can be avoided.
J Thromb Haemost: Journal Metrics Score 3.5, Q1 · cited 530 times
The validation study has been cited 1,457 times, and 449 PubMed articles mention the Wells score for pulmonary embolism in their title or abstract. Citation counts from OpenAlex and article counts from PubMed, retrieved November 15, 2026. Journal Metrics Scores and quartiles are from this site’s current release; follow the journal name for details.
After the result
Shock or hypotension · PE likely (above 4) · PE unlikely (4 or less) · Low probability
Do not use the score. Image without waiting for a D-dimer. Check a D-dimer. Consider PERC.
Next steps
Avoid common errors
5 common errors to avoid
and 3 more
When the score misleads
1“PE most likely” is subjective
It carries 3 points and different clinicians score it differently. Record why you chose it.
2A low score is not zero
In the validation study 1.3% of low-probability patients had pulmonary embolism. The score must be followed by PERC, a D-dimer or imaging.
3Inpatients and pregnancy
The score was validated in outpatients and emergency patients. D-dimer is often raised in hospital inpatients and in pregnancy, and pregnancy-specific pathways exist.
4Surgery means the last 4 weeks
Older operations do not count and should not be scored.
5D-dimer only after the score
Do not order a D-dimer at high probability (above 6), or for “PE likely” on the two-tier pathway: a normal result does not exclude pulmonary embolism there.
Formula
Seven items from 1 to 3 points; below 2 low, 2 to 6 moderate, above 6 high; 4 or less PE unlikely.
Seven items from 1 to 3 points; below 2 low, 2 to 6 moderate, above 6 high; 4 or less PE unlikely.
Items and probability groups
| Item | Points |
|---|---|
| Clinical signs and symptoms of DVTAt least leg swelling and pain on palpation of the deep veins. | 3 |
| Pulmonary embolism is the most likely diagnosisAn alternative diagnosis is less likely than pulmonary embolism, judged from the history, examination, chest X-ray, ECG and blood tests. | 3 |
| Heart rate above 100 per minute | 1.5 |
| Immobilization or recent surgeryBed rest (except to go to the bathroom) for 3 days or more, or surgery in the previous 4 weeks. | 1.5 |
| Previous DVT or pulmonary embolismObjectively diagnosed. | 1.5 |
| Hemoptysis | 1 |
| CancerTreated now or in the previous 6 months, or receiving palliative care. | 1 |
| Probability | Score | Had PE | Patients |
|---|---|---|---|
| Low probability | below 2 | 1.3% | 527 |
| Moderate probability | 2 to 6 | 16.2% | 339 |
| High probability | above 6 | 37.5% | 64 |
| Category | Score | Next step |
|---|---|---|
| PE unlikely | 4 or less | D-dimer; imaging only if raised |
| PE likely | above 4 | CT pulmonary angiography |
Wells 2000
Wells 2001
Pooled prevalence
Test cases
3 published cases, each also a test case
3 published cases; the calculator reproduces every score.
Worked examples
A 51-year-old woman started clozapine for treatment-resistant schizophrenia and over the next two to three weeks, as an inpatient, developed dry cough, fever, lethargy and chest pain. She had no signs of deep vein thrombosis and no risk factors for venous thromboembolism. The only Wells item was a heart rate above 100. She was tested for COVID-19 (negative), treated for a chest infection and screened for clozapine myocarditis; when these were excluded, CT pulmonary angiography showed a subsegmental pulmonary embolism.
“At initial presentation, she had a Wells score of 1.5 for HR >100”
Heart rate above 100 scores 1.5; everything else was absent, including “PE most likely” while infection and myocarditis were suspected. A low score did not exclude a small embolus; her D-dimer was raised.
Entered as: Clinical signs and symptoms of DVT: No (0); Pulmonary embolism is the most likely diagnosis: No (0); Heart rate above 100 per minute: Yes (1.5); Immobilization or recent surgery: No (0); Previous DVT or pulmonary embolism: No (0); Hemoptysis: No (0); Cancer: No (0).
Source: Kwan JY et al., Clin Case Rep 2022 (PubMed · Free full text · DOI)
A man in his early 40s with peripheral arterial disease, inconsistently taking apixaban after an arterial thrombectomy and catheter-directed thrombolysis months earlier, came in with two days of pleuritic chest pain. His heart rate was 123 per minute and D-dimer 2.8 µg/mL FEU; leg ultrasound showed no deep vein thrombosis. CT showed a segmental pulmonary embolism and a pericardial effusion. Persistent pain led to repeat imaging, which found a retained guidewire running from the inferior vena cava into the right atrium, the cause of his pericarditis.
“His Wells’ score was 6, reflecting tachycardia, recent vascular intervention, and pulmonary embolism being more likely than alternative diagnoses.”
PE most likely 3, heart rate 1.5 and the vascular procedure 1.5, as the authors scored it. Strictly, the surgery item covers the previous 4 weeks, and his procedure was several months before; without it the score is 4.5, still above 4 (PE likely) and in the moderate band. The authors themselves describe the procedure as arterial, not one that directly predisposes to venous thromboembolism.
Entered as: Clinical signs and symptoms of DVT: No (0); Pulmonary embolism is the most likely diagnosis: Yes (3); Heart rate above 100 per minute: Yes (1.5); Immobilization or recent surgery: Yes (1.5); Previous DVT or pulmonary embolism: No (0); Hemoptysis: No (0); Cancer: No (0).
Source: Sharma M et al., SAGE Open Med Case Rep 2026 (PubMed · Free full text · DOI)
A 53-year-old man with a BMI of 42 had a quadriceps tendon repair with a thigh tourniquet and tinzaparin prophylaxis for a week afterwards. Four days after stopping it he had right calf discomfort that settled, then sudden left-sided pleuritic chest pain with increasing breathlessness. His Wells score was 9, and CT pulmonary angiography showed a pulmonary embolism at the left lower lobe bifurcation extending into segmental branches.
“Wells' score was 9.”
The authors gave only the total, so this split is inferred. The report excludes previous venous thromboembolism and hemoptysis; the only combination of the remaining items that makes 9 is signs of DVT 3, PE most likely 3, surgery within 4 weeks 1.5 and heart rate above 100 1.5, which also means no cancer. The report does not give his heart rate or describe leg swelling at presentation (his calf discomfort had settled).
Entered as: Clinical signs and symptoms of DVT: Yes (3); Pulmonary embolism is the most likely diagnosis: Yes (3); Heart rate above 100 per minute: Yes (1.5); Immobilization or recent surgery: Yes (1.5); Previous DVT or pulmonary embolism: No (0); Hemoptysis: No (0); Cancer: No (0).
Source: Sudalaimuthu M et al., Cureus 2025 (PubMed · Free full text · DOI)
FAQ
6 questions and answers
and 4 more answers
Questions
Clinical signs of deep vein thrombosis (3 points), pulmonary embolism as the most likely diagnosis (3), heart rate above 100 (1.5), immobilization for 3 days or more or surgery in the previous 4 weeks (1.5), previous DVT or pulmonary embolism (1.5), hemoptysis (1) and cancer (1). The total runs from 0 to 12.5.
Above 6 is high probability; 37.5% of these patients had pulmonary embolism in the 2001 validation study. Below 2 is low (1.3%) and 2 to 6 moderate (16.2%). On the two-tier version, above 4 is “PE likely” and 4 or less “PE unlikely”.
Most pathways now use two tiers. With “PE unlikely” (4 or less) a normal D-dimer excludes pulmonary embolism without imaging; with “PE likely” (above 4) the patient goes to CT pulmonary angiography. The three-tier version gives a finer estimate of probability.
It is the clinician’s judgement after the history, examination and initial tests such as the chest X-ray, ECG and blood count. It carries 3 points, so it moves the score more than any objective item. Decide it before the D-dimer result is known.
The pulmonary embolism rule-out criteria are eight findings (age under 50, heart rate under 100, oxygen saturation 95% or more, no hemoptysis, no estrogen use, no previous VTE, no unilateral leg swelling, no surgery or trauma needing hospital care in the last 4 weeks). In patients the clinician already judges low probability, meeting all eight means no D-dimer is needed.
Yes, in patients with “PE unlikely”, or low or moderate probability. For patients over 50, the cut-off is age × 10 µg/L (fibrinogen-equivalent units), which the 2019 ESC guideline accepts; it lets more older patients avoid imaging.
Further reading
10 references with PubMed and DOI links
10
references
3
free full text
From Wells PS et al., Ann Intern Med 2001 to the newest case reports.
References
clinical grade of aneurysmal subarachnoid hemorrhage, I to V.
total calcium adjusted for albumin, in mg/dL or mmol/L.
stroke severity from 15 bedside items, 0 to 42.
MAP from systolic and diastolic pressure, against the 65 mm Hg target.
eye, verbal and motor scores for preverbal children, 3 to 15.
oxygenation ratio with the Berlin ARDS severity ranges.
serum sodium corrected for high glucose, Katz or Hillier factor.
sodium − (chloride + bicarbonate), with the albumin-corrected gap.
urea nitrogen to creatinine ratio, in US or SI units.
estimated creatinine clearance with actual, ideal or adjusted weight.
cardiac output and index from oxygen consumption and saturations.
ANC from the white cell count, neutrophils and bands.
insulin resistance from fasting glucose and insulin, in US or SI units.
FENa from plasma and urine sodium and creatinine: prerenal, indeterminate or tubular pattern.
three-item stroke severity screen for large vessel occlusion, 0 to 4.
water deficit in hypernatremia from sodium, weight and body water.
expected PaCO2 in metabolic acidosis, 1.5 × HCO3 + 8 ± 2.
corrected QT interval by Bazett, Fridericia, Framingham or Hodges.
head CT decision rule for children with minor head trauma.
blood loss before hemoglobin or hematocrit reaches a chosen lowest value.
eye, verbal and motor response, 3 to 15, with GCS-Pupils.
Devine ideal body weight and adjusted weight from height and sex.
cuffed and uncuffed tube size and oral depth by age.
calculated osmolality, osmolal gap and ethanol correction.
severity of alcohol-associated hepatitis from prothrombin time and bilirubin.
MELD, MELD-Na and MELD 3.0 for chronic liver disease.
early stroke risk after a transient ischemic attack.
whether a patient with blunt trauma needs cervical spine imaging.
prognosis from a Bruce protocol exercise test.
alveolar–arterial oxygen gradient from a blood gas.
whether an adult with minor head injury needs CT.
risk of advanced liver fibrosis from age, AST, ALT and platelets.
6-week risk of a major cardiac event in emergency chest pain.
whether a pleural effusion is an exudate or a transudate.
cardiac risk before major noncardiac surgery, from six factors.
urine output by weight, KDIGO oliguria stage and fluid balance.
Contributed by Dr. Meng Zhao (MD · Former Neurosurgeon · Medical AI Researcher), from the original publications listed here. Last updated November 15, 2026. LinkedIn
The calculator code is tested against every worked example on this page before each release.
This calculator supports, and does not replace, clinical judgment. It is meant for healthcare professionals and is not medical advice for patients. Report an error through the contact page.