PE rules: what are the common themes?

21 Nov

PERC Rule, Well’s Critera

both are clinical decision rules used to identify patients low-risk for PE

breakdown of each rule set below, but here are some common themes in both rule sets for low-risk patients:

  • HR <100
  • No prior history of DVT/PE
  • No recent trauma/immobilization/surgery
  • No hemoptysis
  • No clinical signs/symptoms of DVT (e.g. unilateral leg swelling)

there’s what you learned in medical school, coming back in actual clinical practice

So what else does Well’s Criteria look at?

  • your clinical suspicion: asks if PE is tops on your differential
  • cancer history: treatment within 6 months, or palliative

if you have NONE of these, plus none of the common list from above, then you’re low risk for PE (1.3%)


So what else does the PERC rule lookat?

  • age: <50 (younger is better, apparently)
  • hypoxia: room air 02 sat >94%
  • estrogen: no exogenous estrogen (e.g. OCPs) is lower risk

if these 3 things, + the common 5 from above, are negative = low risk

may miss 1-2% of PEs, but suggested these would be low mortality/low clot burden patients



  • clinical decision rules are low-risk, not NO risk
  • accept some tiny risk of missing something when you use these, at the benefit of not irradiating everyone
  • good luck


References: PERC rule; Well’s Criteria; picture


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