What are the Wells criteria (clinical prediction rule) for deep vein thrombosis (DVT) or pulmonary embolism (PE)?

Wells Criteria for Deep Vein Thrombosis and Pulmonary Embolism

The Wells criteria are validated clinical prediction rules that stratify patients with suspected DVT or PE into probability categories to guide diagnostic testing—they should be calculated as the first step before ordering any diagnostic tests. 1, 2

Wells Criteria Components

For Deep Vein Thrombosis (DVT)

The Wells DVT score assigns points based on clinical features and categorizes patients into low, moderate, or high probability groups, with DVT prevalence ranging from 5% (low), 17% (moderate), to 53% (high) pretest probability. 1 The scoring system includes:

• Active cancer
• Paralysis or recent immobilization of lower extremity
• Recently bedridden >3 days or major surgery within 12 weeks
• Localized tenderness along deep venous system
• Entire leg swelling
• Calf swelling >3 cm compared to asymptomatic leg
• Pitting edema confined to symptomatic leg
• Collateral superficial veins (non-varicose)
• Previously documented DVT
• Alternative diagnosis as likely or more likely than DVT (subtracts points) 1, 2

For Pulmonary Embolism (PE)

The Wells PE score can be used in either a three-level classification (low/moderate/high probability) or two-level classification (PE unlikely/PE likely). 1 When using three-level classification, PE prevalence is approximately 10% in low-probability, 30% in moderate-probability, and 65% in high-probability categories. 1 The two-level classification shows 12% PE prevalence in "PE unlikely" and 30% in "PE likely" categories. 1

Key variables include:

• Clinical signs/symptoms of DVT (3 points)
• PE as likely or more likely than alternative diagnosis (3 points)
• Heart rate >100 bpm (1.5 points)
• Immobilization ≥3 days or surgery in previous 4 weeks (1.5 points)
• Previous PE or DVT (1.5 points)
• Hemoptysis (1 point)
• Malignancy (1 point) 1

Clinical Application Algorithm

Step 1: Calculate Wells Score First

Always calculate the Wells criteria before ordering any diagnostic tests—this is the recommended first step by major guidelines. 1, 2 The pretest probability assessment is essential because post-test probability depends not only on the diagnostic test characteristics but also on the pretest probability. 1

Step 2: Determine Diagnostic Pathway Based on Risk Category

For DVT:

• Low or moderate risk: Proceed to high-sensitivity D-dimer testing first; negative result safely excludes DVT with 99% negative predictive value 1, 2
• High risk: Bypass D-dimer and proceed directly to compression duplex ultrasound 2

For PE:

• PE unlikely (two-level score): Obtain D-dimer; negative result safely excludes PE without imaging 1, 2
• PE likely (two-level score): Proceed directly to CT pulmonary angiography (CTPA) 2
• Low or moderate probability (three-level score): D-dimer testing appropriate; negative result rules out PE 1
• High probability (three-level score): Proceed directly to imaging 1

Important Caveats and Pitfalls

The subjective component is a limitation: The Wells score includes one subjective item ("alternative diagnosis less likely than PE/DVT"), which may reduce inter-observer reproducibility. 1 Despite this, the Wells rule has been extensively validated and performs well in clinical practice. 3, 4

D-dimer has limited utility in certain populations: In patients with cancer, recent surgery, major trauma, or hospitalized patients, D-dimer is frequently elevated regardless of VTE presence, making it less useful. 1 In these situations, bypass D-dimer testing and proceed directly to imaging. 2

Age affects D-dimer specificity: D-dimer specificity decreases with age to approximately 10% in patients >80 years. 1 Consider using age-adjusted D-dimer cutoffs (age × 10 μg/L above 50 years) to improve specificity from 34% to 46% while maintaining >97% sensitivity. 1

Performance varies by clinical setting: The Wells score performs poorly in predicting isolated distal DVT and has reduced utility in hospitalized patients compared to outpatients. 5 One study in DVT patients showed Wells criteria could not predict coexisting PE, suggesting caution against overreliance as the sole decision-making tool in this specific subset. 6

Simplified versions are available: Both the Wells and Geneva scores have been simplified to improve clinical adoption, assigning one point per variable rather than weighted scoring. 1, 4 These simplified versions have been externally validated and perform similarly to the original versions. 1, 4

Alternative: PERC Rule for Very Low Risk PE

The Pulmonary Embolism Rule-out Criteria (PERC) can be applied in emergency department patients with low clinical suspicion to potentially avoid unnecessary testing altogether. 1 PERC includes eight criteria: age <50 years, pulse <100 bpm, SaO2 >94%, no unilateral leg swelling, no hemoptysis, no recent trauma/surgery, no history of VTE, and no oral hormone use. 1 When all PERC criteria are met in low-risk patients, PE can be excluded without D-dimer or imaging. 1