What Is the Wells Score for PE?

The Wells Score for Pulmonary Embolism (PE) is the most widely validated clinical decision tool for estimating pre-test probability of PE in patients presenting with dyspnoea, chest pain, or unexplained hypoxia. Developed by Philip Wells et al. in 2000, it stratifies patients into low, moderate, or high probability groups — directly determining whether D-dimer testing or immediate CT pulmonary angiography (CTPA) is the appropriate next step.

Correct application of the Wells Score prevents both under-investigation (missed PE) and over-investigation (unnecessary radiation, contrast nephropathy, and healthcare costs).

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The 7 Wells PE Criteria — Step by Step

Criterion 1 — Clinical Signs of DVT (+3 Points)

Score 3 points if the patient has objective clinical evidence of deep vein thrombosis:

• •Unilateral leg swelling (calf circumference > 3 cm compared to contralateral leg)
• •Unilateral leg pain with palpation along the deep venous system
• •Pitting oedema greater in the symptomatic leg

Clinical tip: This is the highest-weighted criterion. Even subtle unilateral leg swelling in a patient with dyspnoea should prompt careful DVT assessment. If in doubt, order a compression duplex ultrasound of the leg simultaneously with PE workup.

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Criterion 2 — PE Is the #1 Diagnosis or Equally Likely (+3 Points)

Score 3 points if, after considering all available clinical information, PE is the most likely diagnosis or equally likely as any alternative.

Clinical tip: This is the most subjective criterion and requires clinical gestalt. Common alternative diagnoses to consider: pneumonia, pleuritis, musculoskeletal chest pain, heart failure exacerbation, ACS, pneumothorax. If you genuinely cannot identify a more likely alternative, score 3 points.

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Criterion 3 — Heart Rate > 100 bpm (+1.5 Points)

Score 1.5 points if the resting heart rate is above 100 beats per minute.

Clinical tip: Tachycardia in PE reflects right ventricular strain and sympathetic activation. A resting HR > 100 in a patient with unexplained dyspnoea should always raise PE on the differential. Use the presenting HR, not the HR after anxiolysis or analgesia.

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Criterion 4 — Immobilisation ≥ 3 Days or Surgery in Past 4 Weeks (+1.5 Points)

Score 1.5 points if the patient has:

• •Been immobilised (bed rest with bathroom privileges only) for ≥ 3 consecutive days in the past 4 weeks, OR
• •Undergone any surgical procedure requiring general or regional anaesthesia in the past 4 weeks

Clinical tip: Long-haul flights (> 4 hours) are a common trigger but do not formally score unless combined with immobility. Post-operative PE is the most preventable form — always ask about recent surgery.

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Criterion 5 — Previous PE or DVT (+1.5 Points)

Score 1.5 points if the patient has a documented history of:

• •Pulmonary embolism (confirmed by CTPA, V/Q scan, or pulmonary angiography)
• •Deep vein thrombosis (confirmed by compression ultrasound or venography)

Clinical tip: Prior VTE is one of the strongest independent risk factors for recurrence. A patient with prior PE presenting with new dyspnoea has a substantially elevated pre-test probability regardless of other criteria.

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Criterion 6 — Haemoptysis (+1 Point)

Score 1 point if the patient reports coughing up blood (haemoptysis), even if small in volume.

Clinical tip: Haemoptysis in PE results from pulmonary infarction — it typically occurs 2–3 days after the embolic event, not at presentation. Massive haemoptysis is more suggestive of malignancy, bronchiectasis, or tuberculosis. Any haemoptysis in the context of dyspnoea and pleuritic chest pain should score this criterion.

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Criterion 7 — Active Malignancy (+1 Point)

Score 1 point if the patient has:

• •Active cancer (any malignancy receiving treatment within the past 6 months)
• •Palliative cancer care

Clinical tip: Cancer is one of the most powerful VTE risk factors — Trousseau syndrome (cancer-associated thrombosis) is common. Patients with active malignancy and new dyspnoea should have a low threshold for PE investigation. Note: cancer-associated PE is treated with LMWH or DOACs (rivaroxaban, apixaban) rather than warfarin.

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Try the Live Wells PE Calculator

Calculate your patient's PE pre-test probability in real time:

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Score Interpretation

Two-Tier System (Most Widely Used)

Three-Tier System (Original Wells)

Which system to use? The two-tier system is recommended by most current guidelines (ESC 2019, ACEP) for its simplicity and validated performance. The three-tier system is useful when you want to identify truly low-risk patients for PERC rule application.

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The D-Dimer Decision

D-dimer is a highly sensitive (> 95%) but non-specific test for VTE. Use it strategically:

When to Order D-Dimer

• •Wells ≤ 4 (PE unlikely) — D-dimer is the appropriate next step
• •Low-to-moderate clinical suspicion

When NOT to Order D-Dimer

• •Wells > 4 — proceed directly to CTPA (D-dimer will not change management)
• •High clinical suspicion regardless of score
• •Post-operative patients (D-dimer is always elevated after surgery)
• •Pregnancy (physiologically elevated throughout)
• •Active malignancy (almost always elevated)
• •Recent hospitalisation or major illness

Age-Adjusted D-Dimer Threshold

For patients over 50 years, use the age-adjusted D-dimer threshold:

Age × 10 μg/L (instead of the standard 500 μg/L cutoff)

Example: A 72-year-old patient → threshold = 720 μg/L

This reduces unnecessary CTPA by approximately 14% in older patients without missing clinically significant PE (ADJUST-PE trial).

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The PERC Rule — Eliminating D-Dimer in Very Low Risk

In patients with very low pre-test probability (clinical gestalt < 15%), the PERC rule can eliminate the need for D-dimer entirely. All 8 criteria must be negative:

If all 8 PERC criteria are negative in a low-risk patient → PE prevalence < 2% → no further testing required. Critical caveat: PERC should only be applied when clinical gestalt is genuinely low (< 15% pre-test probability). Do not apply PERC to patients with moderate or high suspicion.

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The YEARS Algorithm — A Simplified Alternative

The YEARS algorithm uses three criteria and a variable D-dimer threshold:

Three YEARS criteria:

• →Clinical signs of DVT
• →Haemoptysis
• →PE as the most likely diagnosis

The YEARS algorithm reduces CTPA by approximately 14% compared to standard Wells + D-dimer (YEARS trial, van der Hulle 2017).

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Diagnosing PE in Special Populations

Pregnancy

• •Wells Score is valid in pregnancy
• •D-dimer is elevated in all trimesters — use trimester-specific thresholds or proceed directly to imaging
• •Preferred imaging: Bilateral leg compression ultrasound first (if positive → treat without CTPA); V/Q scan preferred over CTPA (lower fetal radiation dose); CTPA if V/Q unavailable or non-diagnostic
• •Treatment: LMWH throughout pregnancy (DOACs contraindicated)

Cancer Patients

• •D-dimer is almost always elevated — proceed directly to CTPA if Wells > 2
• •Treatment: LMWH (dalteparin) or DOACs (rivaroxaban, apixaban) preferred over warfarin
• •Duration: Indefinite anticoagulation while cancer is active

Haemodynamically Unstable Patients

• •Do NOT delay treatment for imaging in haemodynamically unstable patients with high clinical suspicion
• •Bedside echocardiography: Right ventricular dilation + McConnell sign supports massive PE
• •Empiric thrombolysis: Consider if CTPA cannot be obtained urgently and clinical suspicion is very high
• •Massive PE treatment: IV alteplase 100 mg over 2 hours (or 0.6 mg/kg over 15 min in cardiac arrest)

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PE Severity Classification and Treatment

ESC 2019 Risk Stratification

Anticoagulation Options

DOACs (preferred for most patients):

• •Rivaroxaban: 15 mg BD × 21 days → 20 mg OD
• •Apixaban: 10 mg BD × 7 days → 5 mg BD
• •Edoxaban: LMWH × 5–10 days → edoxaban 60 mg OD
• •Dabigatran: LMWH × 5–10 days → dabigatran 150 mg BD

LMWH + Warfarin (when DOACs not suitable):

• •Enoxaparin 1 mg/kg BD + warfarin (target INR 2–3)
• •Overlap until INR ≥ 2 for ≥ 24 hours (minimum 5 days LMWH)

Duration:

• •Provoked PE (surgery, immobility): 3 months
• •Unprovoked PE: ≥ 3 months, consider indefinite
• •Cancer-associated PE: Indefinite while cancer active

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Common Wells Score Errors

1. Scoring DVT signs without objective evidence

The DVT criterion requires objective clinical signs (leg swelling, tenderness along deep veins), not just patient-reported leg pain. Bilateral leg oedema from heart failure does not score.

2. Applying D-dimer to high-probability patients

Wells > 4 = proceed directly to CTPA. A negative D-dimer in a high-probability patient does not exclude PE (false negative rate ~5%).

3. Not using age-adjusted D-dimer

In patients over 50, the standard 500 μg/L threshold leads to unnecessary CTPA. Always use age × 10 μg/L in patients ≥ 50 years.

4. Applying PERC to moderate-risk patients

PERC is only valid when clinical gestalt is genuinely < 15%. If you have any moderate suspicion, PERC does not apply.

5. Forgetting haemodynamic instability

In haemodynamically unstable patients with suspected massive PE, do not wait for Wells scoring or D-dimer — treat empirically and image urgently.

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Key References

• •Wells PS et al. Derivation of a simple clinical model to categorize patients probability of pulmonary embolism. *Thromb Haemost.* 2000;83(3):416–420.
• •Konstantinides SV et al. 2019 ESC Guidelines for the diagnosis and management of acute pulmonary embolism. *Eur Heart J.* 2020;41(4):543–603.
• •Kline JA et al. Clinical criteria to prevent unnecessary diagnostic testing in emergency department patients with suspected pulmonary embolism. *J Thromb Haemost.* 2004;2(8):1247–1255.
• •van der Hulle T et al. Simplified diagnostic management of suspected pulmonary embolism (the YEARS study). *Lancet.* 2017;390(10091):289–297.