The pulmonary embolism rule-out criteria (PERC) was designed to identify patients in whom the risk of testing outweighs the benefits (the “test threshold”, which for pulmonary embolism (PE) was calculated as a 2% prevalence).
The PERC consists of eight objective variables that can be applied to patients with low clinical (pre-test) probability of PE. The sensitivity of the PERC rule is 96% to 100% and specificity is 15% to 27%.
Variable
- Age <50 yr
- Pulse <100 bpm
- SaO2 >94%
- No unilateral leg swelling
- No hemoptysis
- No recent trauma or surgery
- No prior pulmonary embolism/ deep venous thrombi
- No hormone use
The PERC rule has not been validated for people with:
- Active cancer, thrombophilia or a strong family history of thrombophilia
- Transient tachycardia or beta-blocker use that may mask tachycardia
- Leg amputations
- Morbid obesity (leg swelling not easily determined)
- Baseline hypoxaemia when oximetry reading <95% is longstanding.
If the patient’s PERC score is >0, then an enzyme-linked immunosorbent assay (ELISA)-type D-dimer is recommended. If this is negative, pulmonary embolism is ruled out and no further investigation is required; if positive, then imaging is recommended.
References:
- Corrigan D, Prucnal C, Kabrhel C. Pulmonary embolism: the diagnosis, risk-stratification, treatment and disposition of emergency department patients. Clin Exp Emerg Med. 2016 Sep 30;3(3):117-125. [Medline]
- Doherty S. Pulmonary embolism An update. Aust Fam Physician. 2017 Nov;46(11):816-820. [Medline]
Created Oct 25, 2019.
