PERC Rule for Pulmonary Embolism
The PERC rule can be applied to patients where the diagnosis of PE is being considered, but the patient is deemed low-risk. A patient deemed low-risk by physician’s gestalt who is also <50 years of age, with a pulse <100 bpm, SaO2 ≥95%, no hemoptysis, no estrogen use, no history of surgery/trauma within 4 weeks, no prior PE/DVT and no present signs of DVT can be safely ruled out and does not require further workup.
The Pulmonary Embolism Rule-out Criteria is utilized by physicians to avoid further testing for Pulmonary Embolism in patients deemed low risk.
- The PERC Rule is a “rule-out” tool - all variables must receive a “no” to be negative.
- The test is unidirectional: while PERC negative typically allows the clinician to avoid further testing, failing the rule doesn't force the clinician to order tests.
- As a rule-out criteria, PERC is not meant for risk-stratification.
- The physicians utilizing this rule must have a gestalt that the patient’s risk of PE is low (study used <15%).
- The study was designed with a 1.8% test threshold. This took into account the risk associated with PE workup and treatment (i.e. CT radiation, anaphylaxis from contrast, bleeding from anticoagulation). For patients with a pre-test probability below this threshold the risk associated with starting a workup is equivalent to the chance of missing the diagnosis.
- Emergency physicians have a low threshold for testing for PE.
- This test rules out patients who are considered low-risk for PE based on clinical criteria alone.
- PERC negative patients do not require utilization of the d-dimer, which has a high sensitivity but low specificity.
- Low risk patients who are PERC negative avoid the risks associated with unnecessary testing and treatment for PE.