PERC Calculator - Pulmonary Embolism Rule-Out Criteria
The PERC calculator (pulmonary embolism rule out criteria) helps you make the right decisions when you suspect pulmon...
What PERC Calculator - Pulmonary Embolism Rule-Out Criteria does
The PERC Calculator estimates the probability of pulmonary embolism in patients with low clinical suspicion, helping clinicians decide whether further testing is needed. A negative result indicates that pulmonary embolism can be ruled out when overall risk is below 2%, potentially allowing D-Dimer testing to be avoided. The tool presents a checklist of clinical criteria that, if absent, support a low-risk assessment. This Omni Calculator version distinguishes itself by offering a clean, step-by-step interface that guides users through each criterion with clear tick-boxes, alongside a prominent disclaimer emphasizing that the tool supplements but never replaces professional medical judgment. It also references the original 2005 validation study and positions itself as a useful supplement to the Wells score rather than a standalone diagnostic. Unlike many clinical calculators, it requires no account or subscription and provides immediate results with sharing options.
How to use the Omni Calculator PERC Calculator - Pulmonary Embolism Rule-Out Criteria
- 1
Select whether the patient is over 50 years old
- 2
Check each applicable PERC criterion: heart rate under 100 bpm, oxygen saturation 94% or above, no unilateral leg swelling, no hemoptysis, no recent trauma or surgery, and no history of venous thromboembolism
- 3
Confirm the clinician's overall impression that pulmonary embolism likelihood is low (less than 15%)
- 4
Review the result indicating whether pulmonary embolism can be ruled out based on the negative PERC score
- 5
Use the share or clear functions to export or reset the calculation as needed
Best for
Emergency physicians, residents, and clinicians evaluating patients with low-probability suspected pulmonary embolism who need a rapid bedside assessment to guide whether D-Dimer testing is necessary.
Limitations
- Designed only for patients with pre-test clinical probability of pulmonary embolism below 15%
- Not valid if any PERC criterion is present; a single positive criterion invalidates the rule-out
- Cannot replace clinical judgment or definitive diagnostic imaging
PERC Calculator - Pulmonary Embolism Rule-Out Criteria FAQ
- What does a negative PERC result mean for my patient?
- A negative PERC result means that if the clinician's overall suspicion for pulmonary embolism is already low (below 15%), the patient's individual risk is further reduced, and pulmonary embolism can be safely ruled out without additional testing.
- Can I use the PERC Calculator on any patient with chest pain?
- No; the PERC rule applies only when the clinician has already estimated the pre-test probability of pulmonary embolism to be less than 15%. If the overall probability is higher, the PERC criteria should not be applied.
- What if one of the PERC criteria is positive?
- If any single PERC criterion is present, the rule no longer applies and the patient cannot be ruled out using this method; further diagnostic testing such as D-Dimer or imaging is required.
- How does this PERC Calculator differ from the Wells score?
- The PERC rule is intended as a supplement to the Wells score for patients with low clinical probability; a negative PERC result can help avoid unnecessary D-Dimer testing, whereas the Wells score stratifies patients into different probability categories to guide testing decisions.
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