Wells' Criteria for Pulmonary Embolism

• Some advocate using the Wells’ Criteria 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 these 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" risk); if using the appropriate D-dimer assay, consider calculating the age adjusted D-dimer.
• 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 below the threshold, PE is ruled out.
  • If the dimer is above the threshold, consider CTPA or V/Q scan. 
• Patient is determined to be moderate risk (score 2-6 points, 16.2% incidence of PE): Consider high sensitivity D-dimer testing or CTPA.
  • If the dimer is below the threshold, PE is ruled out.
  • If the dimer is above the threshold, consider CTPA or V/Q scan.
• Patient is determined to be high risk (score >6 points: 37.5% incidence of PE): Consider CTPA. 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 below the threshold, PE is ruled out.
  • If the dimer is above the threshold, consider CTPA or V/Q scan.
• Patient risk is determined to be “PE Likely” (>4 points, 37.1% incidence of PE): Move directly to confirmatory imaging (CTPA or V/Q scan).

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