Utility of a Clinical Prediction Rule to Exclude Pulmonary Embolism Among Low-Risk Emergency Department Patients: Reason to PERC Up

In this issue of JAMA, Freund and colleagues¹ report the results of the PROPER trial, a cluster-randomized clinical trial conducted at 14 centers in France that tested the effect of a clinical prediction rule, using only clinical criteria, to exclude acute pulmonary embolism (PE) at the bedside among low-risk emergency department patients. These criteria are commonly referred to as the PERC rule (pulmonary embolism rule-out criteria) and consist of 8 objective factors: arterial oxygen saturation (Sp o₂) of 94% or less, unilateral leg swelling, hemoptysis, recent trauma or recent surgery, prior PE or prior deep venous thrombosis, pulse rate of at least 100 beats/minute, patient age of 50 years or older, and exogenous estrogen use. In this trial, the investigators compared patient outcomes from usual emergency care processes vs care processes that included the PERC rule. This study addresses an important clinical controversy—can the notoriously elusive and potentially fatal disease process of PE be safely excluded without laboratory testing or radiological imaging?