The clinical diagnosis of pulmonary embolism (PE) can be challenging given its variable presentation, requiring dependence on objective testing. Decision instruments such as PERC and the Wells’ score help stratify patients to low or high probability, enabling focused use of CT pulmonary angiography (CTPA) for diagnosis. However, despite these algorithms, there is evidence of increasing use of CTPA along with diminishing diagnostic rate (less than 10%). This combination results in the overdiagnosis of subsegmental PEs, unnecessary exposure to radiation, false positive results and the potential for contrast-induced nephropathy. The YEARS study aims to present a simplified algorithm for evaluation with a two-tiered D-dimer threshold to reduce the numbers of CTPA in all age groups.

The YEARS items:

  • Clinical signs of DVT
  • Hemoptysis
  • PE most likely diagnosis

D-Dimer Threshold:

  • Any YEARS items = 500 ng/mL
  • No YEARS items = 1000 ng/mL

Clinical Question

How effective is the YEARS algorithm for diagnosing suspected acute PE and how does it compare with the Wells’ rule and a fixed D-dimer threshold of 500 ng/mL?


Consecutive outpatients and inpatients with suspected acute (first or recurrent) PE


Primary: Number of independently adjudicated events of venous thromboembolism (VTE) during 3 months of follow-up
Secondary: Number of required CTPA in the YEARS algorithm compared to Wells’ diagnostic algorithm


Prospective, multi-center, cohort study


Age less than 18
Initiation of therapeutic anticoagulation 24 hours or more before evaluation
Life expectancy less than 3 months
Geographic inaccessibility precluding follow-up
Allergy to intravenous contrast

Primary Results

Primary Results

  • 3,465 patients enrolled in study, of whom 456 (13%) were diagnosed with PE
    • No YEARS Items present: 55 of 1743 (3.2%)
    • > 1 YEARS items present: 401 of 1722 patients (23%)
  • 2,946 patients were “ruled out” and remained untreated
  • 6 patient deaths, unable to exclude PE as cause of death (0.20%, 95% CI 0.07-0.44)
    • 2 patients managed without CTPA
    • 4 patients managed with CTPA
  • 18 patients diagnosed with symptomatic VTE at 3 months (0.61%, 95% CI 0.36-0.96)
    • 7 patients managed without CTPA
    • 11 patients managed with CTPA

Critical Results

Absolute reduction in CTPA examinations in the YEARS algorithm:

  • Compared to standard Wells’ rule and D-dimer with fixed threshold (<500 ng/mL)
    • Intention-to-diagnose: 13%
    • Per-protocol: 14%
  • Compared to Wells’ rule and age-adjusted D-dimer
    • Intention-to-diagnose: 7.6
    • Per-protocol: 8.7%
  • Patients younger than 50 years: 14%


  • Large numbers of consecutive patients
  • Near complete follow-up
  • Independent adjudication of endpoints


  • Absence of control group
  • Clinicians aware of D-dimer results prior to assessing YEARS items
  • Only hemodynamically stable patients in cohort
  • Autopsy scarcely done, unable to exclude PE as cause of death in six patients
  • PE prevalence higher than observed in North American cohorts
  • Relatively small number of cancer patients, difficult to extrapolate safety of algorithm to this group

Author's Conclusions

“The YEARS diagnostic algorithm safely ruled out acute pulmonary embolism in patients presenting with clinically suspected pulmonary embolism, with a low risk for venous thromboembolism during a 3-month follow-up. The main advantage of the YEARS algorithm is the absolute 14% decrease in the number of CTPA examinations that is applicable to all ages and was shown consistently across subgroups.”

Our Conclusions

This study offers promising data defending the use of a simplified assessment for PE along with a variable D-dimer threshold. However, we have serious concerns about the availability of D-dimer results prior to risk stratification with the YEARS items. Knowledge of the D-dimer results likely influenced the already subjective assessment of whether PE was the “most likely diagnosis”. The cohort in this study also had a higher prevalence of PE than seen in most North American studies. In a population with lower prevalence, the indiscriminant application of a low specificity test like D-dimer risks resulting in increased false negatives and over-testing.

Potential Impact To Current Practice

None at this time. Further study of the YEARS protocol and external validation is needed.

Bottom Line

It is vital to continue research on simplified diagnostic algorithms geared towards reducing over-utilization of CTPA in the workup of PE. But for this algorithm, we recommend waiting for more validation data before incorporating it into our practice.