The Wells score is a clinical prediction tool used to assess the probability of deep vein thrombosis (DVT) or pulmonary embolism (PE), both of which are manifestations of venous thromboembolism (VTE). It helps clinicians estimate the likelihood of these conditions in patients presenting with symptoms and guides further diagnostic testing and management.

There are two versions of the Wells score: one for DVT and one for PE.

Wells Score for Pulmonary Embolism (PE)

The Wells score for PE assigns points to various clinical findings and risk factors to calculate the probability of a patient having a PE. The total score helps classify patients into different risk categories.

PE Wells Score Criteria:

- Clinical signs and symptoms of DVT: 3 points

- Leg swelling, pain, or tenderness along the deep veins.

- Heart rate >100 bpm: 1.5 points

- Immobilization or surgery in the previous 4 weeks: 1.5 points

- Previous history of DVT or PE: 1.5 points

- Hemoptysis (coughing up blood): 1 point

- Active cancer: 1 point

- Cancer treatment within 6 months or palliative treatment.

- PE is the most likely diagnosis (no other alternative explanation for symptoms): 3 points

Interpretation:

- High probability: >6 points (high risk of PE)

- Moderate probability: 2-6 points (moderate risk of PE)

- Low probability: <2 points (low risk of PE)

Some institutions may also use a simplified version:

- PE unlikely: Score ≤ 4

- PE likely: Score > 4

Based on the score, clinicians decide whether to pursue D-dimer testing, CT pulmonary angiography (CTPA), or other imaging studies.

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Wells Score for Deep Vein Thrombosis (DVT)

The Wells score for DVT is similar to the PE score but focused on signs and risk factors associated with a DVT in the legs.

DVT Wells Score Criteria:

- Active cancer: 1 point

- Paralysis, paresis, or recent immobilization of the leg: 1 point

- Recently bedridden for >3 days or major surgery within 12 weeks: 1 point

- Localized tenderness along the deep veins: 1 point

- Swelling of the entire leg: 1 point

- Calf swelling by more than 3 cm compared to the asymptomatic leg: 1 point

- Pitting edema in the symptomatic leg: 1 point

- Collateral superficial veins (non-varicose): 1 point

- Previous history of DVT: 1 point

- Alternative diagnosis at least as likely as DVT: -2 points

Interpretation:

- High probability: ≥3 points

- Moderate probability: 1-2 points

- Low probability: 0 points

Patients with a higher score are more likely to have a DVT and may require further imaging (e.g., compression ultrasonography) or treatment. A D-dimer test may also be used for patients in the moderate- or low-risk categories to rule out DVT.

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Clinical Use:

1. Pulmonary Embolism:

- A low Wells score for PE (≤4) often prompts the use of a D-dimer test to rule out PE. If D-dimer is negative, PE is unlikely.

- A high Wells score for PE (>4) typically leads to immediate imaging with a CT pulmonary angiography (CTPA).

2. Deep Vein Thrombosis:

- For low-risk or moderate-risk patients (≤2), a D-dimer test may be performed, with imaging if the result is positive.

- For high-risk patients (≥3), compression ultrasound is usually the next step.

Summary:

The Wells score for both PE and DVT is a useful tool for estimating the likelihood of venous thromboembolism. It helps clinicians decide on appropriate diagnostic testing and management strategies. The score is easy to calculate, and its integration into clinical pathways improves decision-making in cases of suspected DVT or PE.

Source:

- Wells PS, et al. Evaluation of D-dimer in the diagnosis of suspected deep-vein thrombosis. N Engl J Med. 2003.

- Wells PS, et al. Excluding pulmonary embolism at the bedside without diagnostic imaging: management of patients with suspected pulmonary embolism presenting to the emergency department by using a simple clinical model and D-dimer. Ann Intern Med. 2001.