Pulmonology
PERC rule
The Pulmonary Embolism Rule-out Criteria are eight findings that, when all are absent in a patient already judged low risk, make PE unlikely enough that no further testing is needed. It is a rule-out, and only for low-risk patients.
Enter the values
Result
PERC negative
Rule-out satisfied
In a patient whose clinical gestalt is already low risk, all eight criteria absent means PE can reasonably be excluded without a D-dimer.
PERC only applies when your pretest probability was already low. Applying it to a moderate or high-risk patient is a misuse of the rule.
This calculator is provided for reference and education. It does not replace clinical assessment, examination, current guidelines, local protocol, or professional judgment. Verify every result before acting on it. Nirogix accepts no liability for clinical decisions made using this tool.
The formula
- All eight criteria must be absent. Any one present makes the rule inapplicable.
When to use it
- A patient in whom PE has been considered and clinical judgment already places them at low risk
And when not to
- It is a rule-out in low-risk patients only. It never rules PE in, and it does not apply in pregnancy.
- It is applied after clinical gestalt, not instead of it.
References
- Prospective multicenter evaluation of the pulmonary embolism rule-out criteria — Kline JA et al., Journal of Thrombosis and Haemostasis, 2008
Last reviewed 07/09/2026.
These calculators are free and always will be. We also build Nirogix, a hospital management system for Indian clinics and hospitals. The same calculations are planned inside the consultation record, pre-filled from the chart.