BACKGROUND AND PURPOSE: 

• The Pulmonary Embolism Rule-Out Criteria (PERC), an 8-item set of clinical criteria that serves as a predictive tool, has not been evaluated using a randomized trial (RCT)  
• Each PERC criteria is scores as ‘0’ (no) or ‘+1’ (yes) and a 0 score indicates no further work-up is needed, with a <2% chance of PE  
• Arterial oxygen saturation (Sp02) of ≤94% 
• Pulse rate of at least 100/min 
• Patient age of 50 years or older 
• Unilateral leg swelling 
• Hemoptysis 
• Recent trauma or surgery 
• Prior PE or deep venous thrombosis (DVT) 
• Exogenous estrogen use 
• Freund et al. (JAMA, 2018) aimed to validate the safety of the PERC-based strategy to exclude PE 

METHODS: 

• A noninferiority, crossover cluster randomized controlled trial  
• 14 EDs in France were involved for two 6-month periods separated by a 2-month washout period 
• Patients who came to the ED with a suspicion of PE were eligible  
• Inclusion criteria included  
  • new-onset presence or worsening of shortness of breath or chest pain  
  • Low probability of PE (clinician’s pre-test probability is <15%), based on physicians unstructured impression of risk (low, moderate, or high) 
    • Evidence that unstructured ‘gestalt’ performs as well as structured assessment 
• Each center was randomized to determine sequence of intervention periods 
• During the PERC period, the diagnosis of PE was excluded with a PERC score of 0, with no further follow up  
• During the non-PERC period, usual diagnostic strategy was followed for low level of suspicion for PE 
  • D-dimer testing 
  • If D-dimer testing is positive, computed tomographic pulmonary angiography (CTPA) was performed 
  • If both negative, PE was ruled out and no further follow-up  
• Primary outcome 
  •  Percentage of failure of the diagnostic strategy 
• Secondary outcomes  
  • Rate of CTPA use  
  • Median length of stay in the emergency department 
  • Rate of hospital admission 

RESULTS: 

• 1916 patients were cluster-randomized (mean age 44 years, 980 [51%] women) 
  • 962 were assigned to the PERC group 
  • 954 were assigned to the control group 
  • A total of 1,749 patients completed the trial 
• A PE was diagnosed at initial presentation in  
  • 26 (2.7%) of patients in the control group vs 14 (1.5%) in the PERC group 
    • Mean difference, 1.3% (95% CI, −0.1% to 2.7%; P = .052) 
• Primary outcome: One symptomatic PE (0.1%) at 3 months was diagnosed during follow-up in the PERC group vs none in the control group 
• The proportion of patients undergoing CTPA in the PERC group vs control group was 13% vs 23%  
  • Mean difference, 9.7% (95% CI, 6.1% to 13.2% P < .001) 
• In the PERC group 
  • Median length of emergency department stay rates were significantly reduced  
    • Mean reduction, 36 minutes (95% CI, 4 – 68)  
  • Hospital admission rates were significantly reduced (13% vs 16%)  
    • Mean difference, 3.3% (95% CI, 0.1% to 6.6%) 

CONCLUSION: 

• Among low-risk patients for PE, using the PERC strategy did not result in an inferior rate of thromboembolic events over 3 months 
• Authors point out limitations of this study, including low initial prevalence of PE at 2.7% and may be explained by low average age  
• This study supports the use of PERC for very low-risk patients presenting at the emergency department 
• NOTE: PERC HAS NOT BEEN VALIDATED IN PREGNANCY OR POSTPARTUM

Learn More – Primary Sources: 

Effect of the Pulmonary Embolism Rule-Out Criteria on Subsequent Thromboembolic Events Among Low-Risk Emergency Department Patients The PROPER Randomized Clinical Trial 

Related ObG Topics:

Outcomes and Mode of Delivery in Pulmonary Hypertension

When to Stop Anticoagulation Following a DVT or Pulmonary Embolus?

Which Thrombophilias in Pregnancy Warrant Thromboprophylaxis? 

Use of CT Scans During Pregnancy