Wells PE Score Calculator

How to Use This Calculator

1. Select Yes/No for each Wells PE criterion (scores 1, 1.5, or 3).
2. Both 2-tier and 3-tier results display with workup guidance.
3. 2-Tier + D-Dimer tab: enter D-dimer value and age for age-adjusted cut-off.
4. PERC Rule tab: apply to low-pretest-probability patients only.

Formula

Example

Frequently Asked Questions

• What is the Wells score for PE? ▼
  The Wells score for pulmonary embolism (PE) is the most widely used clinical prediction rule for estimating pretest probability of PE, developed by Wells and colleagues and initially published in 1998, with a major revision in 2000 in Thrombosis and Haemostasis. It uses seven clinical criteria: clinical signs and symptoms of DVT (leg swelling and pain with palpation of deep veins), scored 3 points; PE being the most likely diagnosis or equally likely to an alternative, scored 3 points; heart rate above 100 bpm, scored 1.5 points; immobilisation for 3 or more days or surgery within the past 4 weeks, scored 1.5 points; prior documented DVT or PE, scored 1.5 points; haemoptysis, scored 1 point; and active malignancy (treatment within 6 months or palliative), scored 1 point. Total score ranges from 0 to 12.5. The two-tier classification (most commonly used in North America) defines PE Unlikely as score ≤4 and PE Likely as score >4. The three-tier classification defines low probability as score below 2 (3.6% PE prevalence), moderate probability as 2–6 (20.5% prevalence), and high probability as above 6 (66.7% prevalence). The score guides further diagnostic workup: PE Unlikely patients should have D-dimer testing first; PE Likely patients should proceed directly to CT pulmonary angiography.
• How is Wells used with D-dimer? ▼
  The Wells score is the pretest probability component of a two-step diagnostic algorithm for PE. When the Wells score classifies a patient as PE Unlikely (≤4), a negative D-dimer test effectively excludes PE without the need for CT pulmonary angiography (CT-PA). D-dimer is a sensitive but non-specific marker of fibrin degradation — it is elevated in PE but also in many non-PE conditions (infection, malignancy, surgery, pregnancy). Standard D-dimer cut-off for exclusion is 500 ng/mL (FEU) using high-sensitivity assays. For patients over 50 years, the age-adjusted D-dimer threshold (age × 10 ng/mL) has been validated in the ADJUST-PE study and approved by ESC guidelines: this raises the cut-off for a 65-year-old from 500 to 650 ng/mL, increasing specificity and reducing unnecessary CT-PA without missing clinically significant PE. When the Wells score is PE Likely (>4), D-dimer testing is not useful because even a negative result does not sufficiently lower the post-test probability — CT-PA should be performed directly. Algorithm: Wells ≤4 + negative D-dimer (age-adjusted) → PE excluded, no imaging. Wells ≤4 + positive D-dimer → CT-PA. Wells >4 → CT-PA directly. This algorithm reduces unnecessary imaging by approximately 30–40% compared to universal CT-PA.
• Should I use the 2-tier or 3-tier Wells PE? ▼
  Both the two-tier and three-tier Wells PE classification systems are validated, but they are used in different clinical contexts. The two-tier system (PE Unlikely ≤4 vs PE Likely >4) was validated by Wells et al. (2001) and is the dominant clinical approach in North America, recommended by the American College of Chest Physicians (ACCP) and used in the original PIOPED studies. It is simple and directly actionable: Unlikely → D-dimer; Likely → CT-PA. The three-tier system (Low <2, Moderate 2–6, High >6) is preferred in European practice and endorsed by the ESC 2019 PE guidelines. It provides more granular probability estimates useful in research and can guide the decision of whether to start empirical anticoagulation while awaiting imaging in high-probability patients. PE prevalence in each tier: Low ~4%, Moderate ~21%, High ~67%. The practical choice depends on local protocol and guideline adherence. The two-tier system reduces decision points to a single binary outcome and better matches how most ED physicians frame the workup question. The three-tier system is more appropriate when clinical details are ambiguous and a moderate-probability patient requires careful shared decision-making about empirical treatment. In pregnant patients, both systems apply, though lung scintigraphy (V/Q scan) may be preferred over CT-PA to minimise foetal radiation.
• What is the PERC rule and when can it be applied? ▼
  The Pulmonary Embolism Rule-out Criteria (PERC) is an 8-item clinical decision rule developed by Kline and colleagues to identify emergency department patients with suspected PE in whom the pretest probability is low enough that even D-dimer testing is unnecessary. The 8 PERC criteria are: age under 50, heart rate below 100 bpm, SpO2 at or above 95% on room air, no haemoptysis, no exogenous oestrogen use, no prior DVT or PE, no unilateral leg swelling, and no surgery or trauma in the prior 4 weeks. PERC can only be applied when the physician's gestalt pretest probability of PE is "low" — typically under 15%. If ALL 8 PERC criteria are met (PERC negative) in a low-pretest-probability patient, the post-test probability of PE falls below 2% — below the threshold for which workup is considered to benefit the patient. Studies have shown that PERC-negative patients have a 30-day PE and death rate of approximately 1.4%, considered an acceptable miss rate given the harms of radiation from CT-PA and false-positive D-dimer results. PERC should NOT be applied to moderate or high-pretest probability patients — a positive PERC rule has no clinical value in these groups. ACEP guidelines endorse PERC use for low-probability patients. The PERC rule significantly reduces unnecessary D-dimer testing and CT scanning in the emergency department.
• What is the difference between Wells PE and Wells DVT? ▼
  The Wells score has two distinct and separate versions — one for pulmonary embolism (Wells PE) and one for deep vein thrombosis (Wells DVT) — that are often confused because they share the author's name but use different criteria and cut-offs. The Wells PE score (described above) estimates pretest probability of pulmonary embolism and uses 7 clinical criteria. The Wells DVT score estimates pretest probability of deep vein thrombosis in the lower extremities and uses a different 9-item scoring system: active cancer (+1), paralysis/paresis/recent cast (+1), bedridden >3 days or major surgery within 12 weeks (+1), localised tenderness along the deep venous system (+1), entire leg swelling (+1), calf swelling >3 cm vs the other leg (+1), pitting oedema only in the symptomatic leg (+1), collateral superficial veins (+1), and an alternative diagnosis at least as likely as DVT (−2). Wells DVT classification: score ≤0 = low probability (~3% DVT prevalence); 1–2 = moderate (~17%); ≥3 = high (~75%). For DVT, the diagnostic algorithm is analogous: low/moderate probability + negative D-dimer → DVT excluded; high probability or positive D-dimer → compression ultrasound. In clinical practice it is important to specify which Wells score is being used in documentation. Both scores are endorsed by ACCP and ASH guidelines for their respective conditions.

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