Wells' Criteria for Pulmonary Embolism

• 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) × 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.

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.

• 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.