Wells' Criteria for Pulmonary Embolism (PE)

The Wells score for Pulmonary Embolism (PE), also known as the Wells Criteria, is a fundamental and widely used clinical decision rule to estimate the pre-test probability of a patient having a pulmonary embolism. It is a scoring system designed to risk-stratify patients presenting with symptoms suggestive of PE (such as pleuritic chest pain or sudden onset dyspnea) and to help guide subsequent diagnostic steps, such as ordering a D-dimer or a computed tomography pulmonary angiography (CTPA). The score assigns points based on seven clinical variables: 3 points for clinical signs or symptoms of Deep Vein Thrombosis (DVT), 3 points if PE is the most likely diagnosis or equally likely, 1.5 points for a heart rate over 100 beats per minute, 1.5 points for immobilization of at least 3 days or surgery in the previous 4 weeks, 1.5 points for a previous history of DVT or PE, 1 point for hemoptysis (coughing up blood), and 1 point for malignancy (active cancer or treatment within the last 6 months). The total score is then used to classify the patient. The most commonly used two-tier model classifies patients as either "PE Unlikely" (a total score of 4 or less) or "PE Likely" (a total score greater than 4). This stratification is crucial: in "PE Unlikely" patients, a negative D-dimer test can safely rule out PE, avoiding unnecessary imaging; in "PE Likely" patients, proceeding directly to CT pulmonary angiography is generally recommended.