The RAMER Reviews: Multicenter evaluation of the YEARS criteria in emergency department patients evaluated for pulmonary embolism
Written By: Ellen Chow, MD; Edited by: Timothy Khowong, MD, MSEd
Background:
The accurate diagnosis of pulmonary embolism (PE) is paramount in the Emergency Department, as a missed diagnosis can lead to patient harm and even death. To this end, there have been a multitude of scoring tools and systems that combine patient factors (age, sex, malignancy, vital signs, etc.) to determine the need for objective testing or advanced imaging (d-dimer, CT angiography, VQ scan) to evaluate for the presence of PE. The presence of a positive d-dimer additionally confounds the question as it is known to be a very sensitive but non-specific test. It is usually common practice now to pursue CT angiography of the chest when the D-dimer is positive, which can lead to unnecessary exposure of patients to radiation and spending of hospital resources. A recent prospective observational study examined whether a higher D-dimer threshold could safely rule out PE in patients with a low pretest probability, specifically in those with no YEARS criteria. This could have significant implications for reducing unnecessary imaging, minimizing radiation exposure, and streamlining ED workflows. Here's a breakdown of the study and its potential impact on clinical practice.
Study Objective:
Can a Higher D-Dimer Threshold Be Used for PE Rule-Out?
The central question of the study was: Can a higher D-dimer threshold be used to rule out PE in patients with low pretest probability, as determined by the absence of YEARS criteria?
YEARS criteria refer to three clinical factors:
1. Clinical signs or symptoms of deep vein thrombosis (DVT)
2. Hemoptysis
3. An alternative diagnosis less likely than PE
In patients who did not meet any of the YEARS criteria, a higher D-dimer threshold (1,000 mg/dL vs. the standard 500 mg/dL) was used to determine if further imaging was necessary.
Study Design: Prospective, Observational Study
This was a prospective observational study conducted in 15 emergency departments across the United States from February 2014 to April 2015. The study aimed to determine whether the application of YEARS criteria could allow for a higher D-dimer threshold while maintaining an acceptable safety margin in ruling out PE.
Study Population: Who Was Included and Who Was Excluded?
The study population was ED patients with suspected PE who underwent objective testing to rule in or rule out PE.
Inclusion criteria: Patients who underwent diagnostic workup for PE and met the general clinical criteria for suspected PE.
Exclusion criteria: Patients excluded from the study included those who had already been ruled out for PE (e.g., via PERC rule), those who did not undergo D-dimer testing, those with contraindications to imaging (e.g., contrast allergies or renal impairment), pregnant women, those on anticoagulants for over 24 hours, and patients with a high pre-test probability for PE.
Intervention: YEARS Criteria and D-Dimer Threshold Adjustment
Participants were grouped based on whether they met the YEARS criteria:
No YEARS criteria: These patients had a D-dimer threshold of 1,000 mg/dL for further imaging.
Any YEARS criteria: These patients had a standard D-dimer threshold of 500 mg/dL for further imaging.
The study also investigated the application of a single Wells PE score question- "Are alternative diagnoses less likely than PE?"—which was found to be the most commonly positive criterion among patients assessed using either YEARS or Wells criteria.
Outcome: Diagnosed PE on CTA Imaging
The primary outcome of the study was the diagnosis of PE based on CT pulmonary angiography (CTA), the gold standard imaging test for PE.
Study Results: What Did They Find?
The study included a total of 1,789 patients, with the following key findings:
1. Using the Wells Criteria:
- 64% of patients had a low pretest probability (Wells score <2).
- 53% had a negative D-dimer (<500 mg/dL), and these patients would not require further imaging.
- Among those who had a negative D-dimer, only two (0.2%) were diagnosed with PE—one via initial CTA and one on follow-up.
2. Using YEARS Criteria:
- 67% of patients would not be referred for imaging with a negative D-dimer (either <1,000 mg/dL using YEARS or <500 mg/dL based on the presence of any YEARS criteria).
- Out of these 1,204 patients, 0.5% (six patients) were diagnosed with PE.
- Five cases were diagnosed through initial CTA.
- One case was diagnosed on follow-up.
- Notably, two of these missed PE diagnoses were subsegmental PEs, which are often considered less clinically significant.
The results were statistically significant, demonstrating that the use of a higher D-dimer threshold (1,000 mg/dL) in the absence of YEARS criteria did not result in a significantly higher rate of missed PE diagnoses compared to the standard 500 mg/dL threshold.
Limitations and Biases
As with any observational study, there are several potential biases and limitations:
1. Observer Bias: Since the study was observational, clinicians had the discretion to determine the diagnostic workup for each patient, potentially introducing bias in how the YEARS criteria and D-dimer thresholds were applied.
2. Loss to Follow-Up: There was a 22% loss to follow-up, meaning that any PE diagnoses occurring after discharge in these patients would not be captured.
3. Data Completeness: While the study aimed to include patients undergoing objective testing to rule out PE, there were cases where chest CTA scans were conducted outside the standard D-dimer protocol, which may have affected the results.
Despite these limitations, the authors argue that this reflects real-world clinical practice, where clinicians often make individualized decisions about PE workup based on a combination of clinical gestalt and validated scoring tools.
External Validity and Generalizability
The patient population in this study was largely drawn from EDs in the United States, making the results relatively generalizable to similar settings. However, the study’s observational nature limits the ability to draw firm conclusions about causality or the effectiveness of the intervention in a strictly controlled experimental setting.
Conclusion
The results of this study suggest that for patients with low pretest probability for PE, a higher D-dimer threshold of 1,000 mg/dL could safely rule out PE, without increasing the rate of missed diagnoses beyond an acceptable threshold (2%). This finding is consistent with the original YEARS validation study and could potentially change how we manage patients with suspected PE, leading to:
- Fewer unnecessary CT scans in patients who are at low risk.
- Reduced radiation exposure for patients.
- More efficient use of ED resources, as fewer patients would need to be referred for imaging.
This study adds to the growing body of evidence supporting the use of YEARS criteria and higher D-dimer thresholds in the management of low-risk patients with suspected PE. By safely reducing the number of unnecessary imaging studies, these findings have the potential to improve clinical efficiency, reduce patient radiation exposure, and enhance decision-making in busy ED settings. However, further research, including randomized controlled trials, is needed to confirm these findings and explore the broader applicability of these approaches in different patient populations.
For now, the results seem promising, and emergency physicians should consider these findings when evaluating patients for PE, particularly in light of the growing emphasis on value-based care and appropriate resource utilization in the ED.
References
Anand Swaminathan, "Pregnancy-Adapted YEARS Algorithm for PE – Ready for Prime Time?", REBEL EM blog, August 15, 2019. Available at: https://rebelem.com/pregnancy-adapted-years-algorithm-for-pe-ready-for-prime-time/.
Anand Swaminathan, "The YEARS Study – Simplified Diagnostic Approach to PE", REBEL EM blog, September 28, 2017. Available at: https://rebelem.com/the-years-study-simplified-diagnostic-approach-to-pe/.
Freund, Yonathan, et al. "Effect of a diagnostic strategy using an elevated and age-adjusted D-dimer threshold on thromboembolic events in emergency department patients with suspected pulmonary embolism: a randomized clinical trial." Jama 326.21 (2021): 2141-2149.
Kabrhel, Christopher, et al. "Multicenter evaluation of the YEARS criteria in emergency department patients evaluated for pulmonary embolism." Academic Emergency Medicine 25.9 (2018): 987-994.
Van der Hulle, Tom, et al. "Simplified diagnostic management of suspected pulmonary embolism (the YEARS study): a prospective, multicentre, cohort study." The Lancet 390.10091 (2017): 289-297.
Van Der Pol, Liselotte M., et al. "Pregnancy-adapted YEARS algorithm for diagnosis of suspected pulmonary em