Safe Ways to Rule Out Pulmonary Embolism without Using a CT Pulmonary Angiogram

by Joseph Esherick, M.D., FAAFP, FHM

Pulmonary embolism (PE) is one of the most difficult to diagnose and potentially fatal disorders in medicine.  Because of this, CT pulmonary angiograms (CTPA) are over utilized so as to not miss this potentially fatal problem.  There are three ways to safely exclude PE:  the use of the PERC tool, the use of age-adjusted D-dimer, and now the YEARS algorithm.

A new study out of the Netherlands prospectively tested a new diagnostic algorithm (YEARS) combining d-dimer concentration with three criteria of the Wells score: signs of deep vein thrombosis (DVT), hemoptysis, and PE the most likely diagnosis. Patients with none of these criteria and a d-dimer level <1000 ng/mL and patients with at least one of the criteria and a d-dimer level <500 ng/mL were considered not to have PE and were managed without CTPA. All other patients underwent CTPA.

The study enrolled 3465 consecutive nonpregnant patients with suspected PE from 12 hospitals in the Netherlands.  Overall, 13% were diagnosed with PE at the initial evaluation. Among 2946 patients in whom PE was initially excluded by the algorithm, 18 (0.61%) had symptomatic deep venous thrombosis (DVT) or PE in the 3 months following evaluation (the primary outcome), and 6 (0.20%) had fatal PE.

The authors calculated that CTPA was avoidable in 48% of patients with this algorithm, compared with 34% if a standard approach (Wells score and d-dimer level <500 ng/mL) had been used and 39% if Wells score and age-adjusted d-dimer threshold had been used.

The PERC rule (PE rule out criteria) is used in the ER to exclude PE in patient's with a low pre-test probability for PE.  It should not be used for patients with an intermediate-high pre-test probability for PE.  For such patient's the presence of the following eight criteria safely excludes a PE:

  • age < 50 years
  • pulse < 100 beats min
  • SaO2 >or= 95%
  • no hemoptysis
  • no estrogen use
  • no surgery/trauma requiring hospitalization within 4 weeks
  • no prior venous thromboembolism (VTE)
  • no unilateral leg swelling

In summary, a PE can be safely excluded without the use of a CTPA if:

  • Absent signs of deep vein thrombosis (DVT), no hemoptysis, and PE NOT the most likely diagnosis and a d-dimer level <1000 ng/mL
  • Patients with at least one of the criteria and a low age-adjusted d-dimer level
  • Negative PERC rule

woman with a pulmonary embolism