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.
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From the Creator
Dr. Kline's comments about the PERC Rule for MDCalc:
“I derived the PERC rule to give some objective backing to the situation where you have considered PE in the active differential diagnosis, but really do not think any diagnostic test is necessary. To capture that concept scientifically, I validated the PERC rule to exclude PE with a gestalt pretest probability of <15% for PE and all eight criteria of the PERC rule are negative.”
About the Creator
Jeffrey Kline, MD, is a professor of emergency medicine and physiology and the vice chair of research at Indiana University. Among other research, he has conducted clinical studies using breath-based methods to diagnose and assess the severity of PE. He co-founded BreathQuant Medical Systems Inc to advance practical applications of 16 patents for medical devices. Dr. Kline has published over 50 manuscripts in the area of PE.
To view Dr. Jeffrey Kline's publications, visit PubMed