Today's Essential Evidence Episode discusses the paper that derived and validated the PE Rule-out Criteria or PERC rule.\xa0 This is a clinical decision aid that we can use to reliably exclude pulmonary embolism in emergency department patients without any further testing.\xa0 We'll talk about some background on diagnosing PE in the ED, the study design, how to use the PERC rule in your everyday practice, and some clinical pearls as well.