Is there a Pulmonary Embolism Rule-out Criteria (PERC) equivalent for patients over 50 years old?

Age-Adjusted D-Dimer Testing is the PERC Equivalent for Patients Over 50 Years Old

For patients over 50 years old, age-adjusted D-dimer testing (age × 10 ng/mL) is the recommended equivalent to PERC, as it maintains high sensitivity while significantly improving specificity for pulmonary embolism diagnosis. 1

Understanding PERC and Its Age Limitation

• The Pulmonary Embolism Rule-out Criteria (PERC) is designed specifically for patients under 50 years old, as age < 50 is one of its eight criteria 1
• PERC allows clinicians to safely rule out PE without further testing when all eight criteria are met in low-risk patients 2
• The eight PERC criteria include: age < 50 years, heart rate < 100 beats/min, oxygen saturation ≥ 95%, no unilateral leg swelling, no hemoptysis, no recent trauma/surgery, no history of VTE, and no hormone use 1

Age-Adjusted D-dimer: The Solution for Older Patients

• The specificity of standard D-dimer testing (500 ng/mL cutoff) decreases steadily with age, dropping to only 10% in patients over 80 years 1
• For patients over 50 years old, using an age-adjusted D-dimer cutoff (age × 10 ng/mL) maintains high sensitivity while significantly improving specificity 1
• A multinational prospective management study validated this approach, showing that age-adjusted D-dimer increased the number of patients in whom PE could be excluded from 6.4% to 30% without additional false-negative findings 1

Specificity Improvements with Age-Adjusted D-dimer

• Age-adjusted D-dimer testing increases specificity across all older age groups 1:
  • Ages 51-60: specificity increases from 57.6% to 62.3% 1
  • Ages 61-70: specificity increases from 39.4% to 49.5% 1
  • Ages 71-80: specificity increases from 24.5% to 44.2% 1
  • Ages >80: specificity increases from 14.7% to 35.2% 1

Diagnostic Algorithm for Patients Over 50

1. Assess pretest probability using validated tools (Wells score or revised Geneva score) 1
2. For low or intermediate pretest probability patients over 50 years:
   • Apply age-adjusted D-dimer cutoff (age × 10 ng/mL) 1
   • If D-dimer is below the age-adjusted threshold, PE can be safely excluded 3
   • If D-dimer is above the threshold, proceed to CTPA 3
3. For high pretest probability patients:
   • Proceed directly to CTPA regardless of D-dimer results 3

Common Pitfalls to Avoid

• Don't apply PERC to patients over 50 years old, as age < 50 is a required criterion 1, 2
• Don't use PERC in patients with intermediate or high pretest probability of PE, regardless of age 1, 2
• Don't rely on standard D-dimer cutoffs (500 ng/mL) for older patients, as this leads to unnecessary imaging due to poor specificity 1, 3
• Don't use point-of-care D-dimer assays when laboratory-based tests are available, as they have lower sensitivity (88% vs. 95%) 1

Alternative Approaches for Special Populations

• For patients with recurrent symptoms and multiple prior CTs, consider lower-extremity venous ultrasonography or V/Q scanning when appropriate 1
• For pregnant patients in the first trimester, consider lower-extremity venous ultrasonography before CT to reduce radiation exposure 1
• For patients with contraindications to CTPA, V/Q scanning remains a viable alternative 3