PERC is a tool that rules out pulmonary embolism (PE) and is an alternate to sensitive D-dimer testing in patients with a low-probability assessment for PE. It is best used in patients who present to the emergency department (ED) with dyspnea or chest pain, in whom the gestalt estimate pre-test probability for PE is less than 15%. It is not meant for risk stratification.

The PERC rule has 8 criteria:

1. Age <50 years
2. Heart rate <100 beats/minute
3. Oxyhemoglobin saturation ≥95%
4. No hemoptysis
5. No estrogen use
6. No prior DVT or PE
7. No unilateral leg swelling
8. No surgery/trauma requiring hospitalization within the prior 4 weeks

In patients with a low probability of PE who fulfill all the above 8 criteria, the likelihood of PE is low and no further testing is required.