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    • Subcategory of 'Diagnosis' designed to be very sensitiveRule Out
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    Wells' Criteria for Pulmonary Embolism

    Objectifies risk of pulmonary embolism.
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    Advice

    • Some advocate using the Wells’ score over clinician gestalt to predict who is low-risk and then applying the PERC rule to stop workup for PE.
    • As with all clinical decision aids, the physician must first have a suspicion of the diagnosis before attempting to apply the Wells criteria.
    • The original intent of this tool was to determine who was low risk enough to rule out testing with a d-dimer.
    • Age adjusted d-dimer cutoffs have been validated for use in patients over 50 years in low risk patients (rGeneva “not high” or Wells’ low). If using the appropriate d-dimer assay consider calculating the age adjusted d-dimer cutoff of: Age (years) x 10 µg/L = cutoff (for patients > 50 years).
    • While both two and three tier models are accepted, guidelines appear to favor the two tier model which utilizes only the high sensitivity d-dimer and more conservative risk stratification; “intermediate” risk patients are thought to be still too high risk to be evaluated without further risk stratification.

    Management

    Three Tier Model

    • Patient is determined to be low risk (<2 points:1.3% incidence PE): consider d-dimer testing to rule out Pulmonary embolism. Alternatively consider a rule-out criteria such as PERC.
      • If the dimer is negative consider stopping workup.
      • If the dimer is positive consider CTA.
    • Patient is determined to be moderate risk (score 2-6 points, 16.2% incidence of PE): consider high sensitivity d-dimer testing or CTA.
      • If the dimer is negative consider stopping workup.
      • If the dimer is positive consider CTA.
    • Patient is determined to be high risk (score >6 points: 37.5% incidence of PE): consider CTA. D-dimer testing is not recommended.

    Two Tier Model

    • Patient risk is determined to be “PE Unlikely” (0-4 points, 12.1% incidence of PE): consider high sensitivity d-dimer testing.
      • If the dimer is negative consider stopping workup.
      • If the dimer is positive consider CTA.
    • Patient risk is determined to be “PE Likely” (>4 points, 37.1% incidence of PE): consider CTA testing.

    Critical Actions

    • Given the next generation d-dimer high sensitivity but low specificity (approx 50%), patients who are considered high risk should be ruled out with CTA.
    • Never delay resuscitative efforts for diagnostic testing, especially in the unstable patient.
    • History and exam should always be performed prior to diagnostic testing.
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