Validation of a clinical algorithm to identify low-risk patients with pulmonary embolism

Background: We previously derived a clinical prognostic algorithm to identify patients with pulmonary embolism (PE) who are at low risk of short-term mortality and who could be safely discharged early or treated entirely in an outpatient setting. Objectives: To externally validate the clinical prognostic algorithm in an independent patient sample. Methods: We validated the algorithm in 983 consecutive patients prospectively diagnosed with PE at an emergency department of a university hospital. Patients with none of the algorithm's 10 prognostic variables (age 70 years, cancer, heart failure, chronic lung disease, chronic renal disease, cerebrovascular disease, pulse 110 min(-1), systolic blood pressure < 100 mmHg, oxygen saturation < 90%, and altered mental status) at baseline were defined as being at low risk. We compared 30-day overall mortality among low-risk patients, on the basis of the algorithm, between the validation sample and the original derivation sample. We also assessed the rate of PE-related and bleeding-related mortality among low-risk patients. Results: Overall, the algorithm classified 16.3% of patients with PE as being at low risk. Mortality at 30 days was 1.9% among low-risk patients, and did not differ between the validation sample and the original derivation sample. Among low-risk patients, only 0.6% died from definite or possible PE, and 0% died from bleeding. Conclusions: This study validates an easy-to-use, clinical prognostic algorithm for PE that accurately identifies patients with PE who are at low risk of short-term mortality. Patients who are at low risk according to our algorithm are potential candidates for less costly outpatient treatment.