Clinical meaning
The Wells scoring systems are validated clinical prediction rules that estimate pre-test probability of deep vein thrombosis (DVT) and pulmonary embolism (PE), guiding the clinician's diagnostic workup. For DVT, the Wells score incorporates: active cancer (+1), paralysis or recent immobilization of lower extremity (+1), recently bedridden >3 days or major surgery within 12 weeks (+1), localized tenderness along deep venous system (+1), entire leg swelling (+1), calf swelling >3 cm compared to asymptomatic leg (+1), pitting edema confined to symptomatic leg (+1), collateral superficial veins (+1), and previously documented DVT (+1), with alternative diagnosis as likely or more likely than DVT (-2). Scores classify patients as low probability (0), moderate (1-2), or high (>=3). For PE, the Wells score includes: clinical signs/symptoms of DVT (+3), PE is the most likely diagnosis (+3), heart rate >100 bpm (+1.5), immobilization or surgery in previous 4 weeks (+1.5), previous DVT/PE (+1.5), hemoptysis (+1), active cancer (+1). PE probability: low (<2), moderate (2-6), high (>6). The clinical significance lies in determining the diagnostic pathway. In low-probability patients, a negative high-sensitivity D-dimer effectively excludes VTE (negative predictive value >99%), avoiding unnecessary imaging. D-dimer should NOT be used to rule out VTE in high-probability patients because false-negative results are unacceptable given the high pre-test probability. High-probability patients proceed directly to imaging: CT pulmonary angiography (CTA) for PE or compression ultrasonography (duplex US) for DVT. The age-adjusted D-dimer threshold (age x 10 mcg/L for patients >50 years) improves specificity in older adults without sacrificing sensitivity. Once VTE is confirmed, anticoagulation is initiated immediately unless contraindicated.