Pulmonary embolism (PE) is a potentially life-threatening clinical condition that occurs when there is a disruption to blood flow in the pulmonary artery or its branches by a thrombus that originated elsewhere in the body, usually from a deep vein thrombosis (DVT), but it can also occur due to embolization from other material into the pulmonary circulation such as air, fat, or tumor cells. PE can present variably and nonspecifically, with findings that include but are not limited to cough, shortness of breath, tachycardia, pleuritic chest pain, hemoptysis, presyncope, syncope, and even hemodynamic instability and cor pulmonale. The risk of mortality from PE is up to 30% in untreated PE and 8% in PE with timely treatment. Furthermore, PE is associated with 100,000 deaths in the United States annually. Therefore, early recognition is crucial to prevent drastic complications.
Several risk scores have been developed to assist in the recognition of PE. The Pulmonary Embolism Rule-out Criteria (PERC), initially created in 2004, derived a scoring system using 8 important variables to allow the clinician to rule out PE if no criteria are positive and the pretest probability is <15% with the goal of decreasing unnecessary testing for PE in emergency room settings. The Geneva Criteria is similar, using 8 objective variables, to help predict the likelihood of PE on presentation. Lastly, one of the most commonly used scores is the Wells criteria for pulmonary embolism, which objectifies the risk of PE using seven variables: clinical signs and symptoms of DVT, PE is the most likely diagnosis or equally likely, heart rate >100 beats per minute, immobilization of at least 3 days or surgery in the previous 4 weeks, previous objectively diagnosed PE or deep vein thrombosis, hemoptysis, and malignancy with treatment within 6 months or palliative. This particular scoring system and the clinical variables selected were validated in a study after logistic regression analysis was performed on 40 clinical variables with these 7 prospectively validated in inpatients and outpatients with suspected PE as they were determined to have the highest odds ratios of all the variables analyzed.