🧭 REBEL Rundown
📌 Key Points
- 👉 Start with Wells if you’re unsure – It helps establish pretest probability and guides next steps.
- 🔍 Use PERC only for low-risk patients – Either based on clinical judgment or a low-risk Wells score.
- 🚫 Don’t use PERC in moderate/high-risk patients – It can lead to false reassurance and missed PE.
- 🧪 D-dimer matters – Use a high-sensitivity assay, especially for moderate-risk patients.
- 📊 Two-tier Wells model is preferred – It’s simpler, aligns with guidelines, and avoids the gray zone of “intermediate” risk.
- 👉 Click here to access the PERC RULE on MDCalc
- 👉 Click here to access the Wells’ Criteria on MDCalc
🤕 Case
A 35 year old woman with no past medical history presents to the ED with pleuritic chest pain and shortness of breath. She is tachypenic but has a normal heart rate and oxygen saturation. She denies leg pain or swelling, or history of DVT/PE. She uses oral contraceptives. Her EKG is normal. Cardiac, lung, and extremity exam are unremarkable. You are considering using the Wells Criteria and/or PERC rule. Where do you start?
🔨 Why Do We Need a Clinical Decision Rule?
Diagnosing PE in the emergency department is tricky. The symptoms—chest pain, shortness of breath, tachycardia—are nonspecific and overlap with many other conditions. But missing a PE can have devastating consequences, so there’s often a low threshold to order a CTA chest. Which leads to over-testing, radiation exposure, contrast risk, increased length of stay, and unnecessary healthcare costs.
The Wells’ Criteria and PERC rule help clinicians safely identify which patients actually need further workup. These tools provide a standardized approach, and—when used appropriately—minimize unnecessary testing without missing clinically significant PEs.
🎯 Quick Hits
💬 Case Resolution
You determine that your patient is low risk by Wells’ Criteria, and proceed to PERC rule. As she is on OCP’s, PE cannot be excluded using PERC rule. So, you order a d-dimer and it comes back negative. Her symptoms resolve upon re-evaluation and you safely discharge her!
🚨 Clinical Bottom Line
When applied appropriately, both tools can help reduce unnecessary imaging. Start with the Wells Criteria if you’re unsure about the likelihood of PE. Use PERC only if you’re already thinking “this patient probably doesn’t have a PE,” or if Wells determines your patient to be low risk. Applying PERC in someone at moderate or high risk can lead to false reassurance—and a missed diagnosis.
Post Peer Reviewed By: Marco Propersi, DO (Twitter/X: @Marco_Propersi), and Mark Ramzy, DO (X: @MRamzyDO)
🧭 Cheat Sheets
- Created July 28, 2025
- Thoracic and Respiratory
- DOWNLOAD
- Created July 28, 2025
- Thoracic and Respiratory
- DOWNLOAD
👤 Author
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