Pulmonary Embolism Rule-Out Criteria and Subsequent Thromboembolic Events

Study Questions:

How effective is the pulmonary embolism rule-out criteria (PERC) to rule out pulmonary embolism (PE)?


The authors performed a crossover cluster-randomized clinical noninferiority trial in 14 emergency departments (ED). Patients with a low gestalt clinical probability of PE were included between August 2015 and September 2016. During the PERC period, a patient was considered to have no PE if all eight PERC elements were negative. The primary outcome was the occurrence of a thromboembolic event during the 3 months following the ED visit. Secondary outcomes included the rate of computed tomographic pulmonary angiography (CTPA), median length of stay in the ED, and rate of hospitalization.


Among 1,916 patients who were cluster-randomized, 962 were assigned to the PERC group and 954 were assigned to the control group (usual care). One PE (0.1%) was diagnosed during the follow-up period in the PERC group versus none in the control group. The proportion of patients undergoing CTPA was lower in the PERC group versus usual care (13% vs. 23%, p < 0.001). Patients in the PERC group had a shorter ED length of stay (mean reduction, 36 minutes; 95% confidence interval [CI], 4-68 minutes) and were hospital admissions (difference of 3.3%; 95% CI, 0.1%-6.6%).


The authors concluded that patients presenting to the ED with very-low risk of suspected PE can be safely ruled out for PE by using the PERC rule.


This prospective, randomized trial supports the safety and efficacy of the PERC rule for ruling out acute PE in the ED for young patients with a low clinical gestalt for acute PE. Use of this rule was also associated with fewer CTPA tests and shorter ED length of stay. In patients without any of the following PE risk factors, acute PE can be effectively ruled out: oxygen saturation ≤94%, pulse ≥100 bpm, age ≥50 years, unilateral leg swelling, hemoptysis, recent trauma or surgery, prior PE or deep vein thrombosis, or exogenous estrogen use. This rule can be useful for younger patients (<50 years old) with low clinical gestalt for acute PE to reduce the burden of CTPA.

Clinical Topics: Anticoagulation Management, Invasive Cardiovascular Angiography and Intervention, Noninvasive Imaging, Prevention, Pulmonary Hypertension and Venous Thromboembolism, Vascular Medicine, Anticoagulation Management and Venothromboembolism, Interventions and Imaging, Interventions and Vascular Medicine, Angiography, Computed Tomography, Nuclear Imaging

Keywords: Angiography, Anticoagulants, Emergency Service, Hospital, Estrogens, Hemoptysis, Pulmonary Embolism, Risk Factors, Secondary Prevention, Thromboembolism, Tomography, X-Ray Computed, Venous Thromboembolism, Vascular Diseases

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