see also Ix of suspected PE

• MDCalc online calculator
• determine if any risk factors present: (as per Wells 1998)
  • surgery within 12wks
  • immobilisation (complete bed rest) for 3 or more days in 4wks prior
  • previous DVT or objectively diagnosed PE
  • strong FH DVT/PE with at least 2 family members or a 1st degree relative with hereditary thrombophilia
  • cancer - Rx ongoing, within past 6mths, or in palliative stages
  • post-partum period
  • lower extremity paralysis
• then determine which category of clinical features of PE pt is in - either “typical severe”, “typical non-severe” or “atypical”: (as per Wells 1998)
  • typical features of PE:
    • at least 2 respiratory points:
      • SOB or worsening chronic SOB;
      • pleuritic chest pain
      • chest pain that is non-retrosternal & non-pleuritic
      • SaO2 < 92% on room air that corrects with oxygen supplementation < 40% FiO2
      • haemoptysis
      • pleural rub
    • and either:
      • HR > 90
      • leg symptoms
      • low-grade fever
      • CXR compatible with PE
    • does pt also have “severe features”:
      • any of:
        • syncope
        • BP < 90mmHg with HR > 100
        • is receiving ventilation or needs FiO2 > 40%
        • new onset RH failure (elevated JVP & new S1Q3T3 or RBBB)
      • if severe features then:
        • if alternative diagnosis less likely than PE ⇒ “high probability”
        • if alternative diagnosis as likely or more likely than PE ⇒ “moderate probability”
      • if no severe features then:
        • if alternative diagnosis as likely or more likely than PE:
          • no risk factor ⇒ “low probability”
          • risk factor ⇒ “moderate probability”
        • if alternative diagnosis less likely than PE:
          • no risk factor ⇒ “moderate probability”
          • risk factor ⇒ “high probability”
  • atypical for PE (ie. not typical as defined above):
    • if alternative diagnosis as likely or more likely than PE:
      • no risk factor ⇒ “low probability”
      • risk factor ⇒ “low probability”
    • if alternative diagnosis less likely than PE:
      • no risk factor ⇒ “low probability”
      • risk factor ⇒ “moderate probability”
• “low pre-test probability” = 3.4% (2.5-5%) probability of PE
  • ie. either:
    • typical features without severe features & alternative diagnosis as likely or more likely than PE and no risk factors
    • no typical features and either:
      • no risk factors, or,
      • alternative diagnosis as likely or more likely than PE
• “moderate pre-test probability” = 27.8% (23-32%) probability of PE
  • ie. either:
    • typical features with severe features but alternative diagnosis as likely or more likely than PE
    • typical features without severe features and either:
      • alternative diagnosis as likely or more likely than PE but risk factors for PE
      • alternative diagnosis less likely than PE but no risk factors
    • no typical features but risk factors & alternative diagnosis less likely than PE
• “high pre-test probability” = 78.4% (69-86%) probability of PE
  • ie. typical features and either:
    • severe features, or
    • no severe features but alternative diagnosis less likely than PE & risk factors present