Introduction: The Diagnostic Burden of Pulmonary Embolism
Pulmonary embolism (PE) remains one of the most challenging diagnoses in emergency medicine due to its non-specific clinical presentation. While computed tomography pulmonary angiography (CTPA) is the gold standard for diagnosis, its overuse carries significant risks, including radiation exposure, contrast-induced nephropathy, and the identification of clinically insignificant subsegmental emboli. To mitigate these risks, clinicians utilize D-dimer testing as a high-sensitivity, low-specificity screening tool. However, the traditional fixed threshold of 500 ng/mL often leads to unnecessary imaging, particularly in elderly patients or those with comorbid conditions that naturally elevate D-dimer levels.
Over the last decade, strategies such as age-adjusted thresholds and the YEARS algorithm have been introduced to increase the specificity of D-dimer testing. Despite their validated safety, adherence in busy clinical environments remains suboptimal due to the perceived complexity of multi-step decision rules. The study by Roussel et al., recently published in the Lancet Respiratory Medicine, explores whether a simplified, single-question approach can achieve similar safety while improving clinical utility.
The Evolution of D-Dimer Strategies
Historically, any D-dimer value above 500 ng/mL necessitated imaging if PE could not be ruled out by clinical criteria alone (such as the PERC rule). The ADJUST-PE study revolutionized this by validating age-adjusted thresholds (age × 10 ng/mL for patients over 50). Subsequently, the YEARS study demonstrated that patients with no clinical signs of PE could safely have their threshold raised to 1000 ng/mL.
Despite these advancements, many clinicians still rely on a “Gestalt” impression. The core question addressed by Roussel and colleagues is whether we can skip the formal score counting and simply ask: “Is pulmonary embolism the most likely diagnosis?”
Study Design and Methodology
This prospective, multicenter, open-label, single-arm interventional study was conducted across 13 emergency departments in France. The researchers aimed to evaluate a simplified diagnostic strategy that applies a 1000 ng/mL D-dimer threshold when PE is not considered the most likely diagnosis, and an age-adjusted threshold when it is.
Patient Selection
The study included 1,221 patients aged 18 years or older who presented with a clinical suspicion of PE. Exclusion criteria were rigorous to ensure safety, excluding patients on full-dose anticoagulation, those with a thromboembolic event in the preceding six months, and those with a life expectancy of less than three months.
The Intervention
The diagnostic algorithm was structured as follows:
1. The treating physician answered the primary question: Is PE the most likely diagnosis?
2. If the answer was “No”: PE was ruled out if the D-dimer was < 1000 ng/mL.
3. If the answer was "Yes" (or if the patient was considered high probability): PE was ruled out if the D-dimer was below the age-adjusted threshold (500 ng/mL if < 50 years; age × 10 ng/mL if ≥ 50 years).
4. Patients exceeding these thresholds proceeded to chest imaging (CTPA or lung scintigraphy).
Primary Endpoints
The primary safety outcome was the diagnostic failure rate, defined as the occurrence of a symptomatic venous thromboembolic event (VTE) during a three-month follow-up period among patients in whom PE was initially ruled out.
Key Findings: Safety and Efficiency
The results of the study provide compelling evidence for the safety of this simplified approach. Of the 1,221 patients included, 997 (81.7%) were categorized as having PE as an “unlikely” diagnosis based on the single question.
Safety Outcomes
Among the patients where PE was ruled out at the initial visit, the diagnostic failure rate at three months was 0.00% (95% CI 0.00–0.34). Even after applying multiple imputation to account for 33 patients lost to follow-up, the failure rate remained exceptionally low at 0.12% (95% CI 0.01–0.55). Both figures were well within the predefined safety margin of 1.85%. This indicates that the simplified threshold is as safe as more complex, validated algorithms.
Impact on Imaging Rates
One of the most significant findings was the reduction in diagnostic imaging. The simplified strategy resulted in a chest imaging rate of 32% (384 of 1,217 patients). When compared to the traditional fixed 500 ng/mL threshold strategy, which would have required imaging in 50% of these patients, the simplified approach achieved an absolute reduction in imaging of 19% (95% CI 16–21). This reduction is clinically significant, representing nearly one in five patients being spared unnecessary radiation and hospital resources.
Expert Commentary and Clinical Implications
The implications of this study for emergency medicine are profound. By validating that a single clinical question—which essentially captures the clinician’s “Gestalt”—can safely guide the D-dimer threshold, this study paves the way for a more intuitive diagnostic process.
The Power of Clinical Gestalt
The study reinforces the value of physician intuition when structured through a standardized threshold. Using “PE most likely” as a pivot point mirrors how many experienced clinicians already think. However, by formalizing it into a 1000 ng/mL cutoff for the “unlikely” group, the study provides the legal and scientific framework necessary for widespread adoption.
Strengths and Limitations
A major strength of the study is its prospective, multicenter design involving various types of hospitals, which enhances the generalizability of the results. The inclusion of patients with a high probability of PE—often excluded from D-dimer studies—adds further weight to the findings.
However, the study is not without limitations. As an open-label, single-arm study, there is a risk of bias in how clinicians answered the primary question. Furthermore, the prevalence of PE in the study population was 7%, which is relatively low compared to some other cohorts. In populations with a significantly higher prevalence of PE, the safety of the 1000 ng/mL threshold might require further validation.
Conclusion: A New Standard for the Emergency Department?
The Roussel et al. study successfully demonstrates that a global simplified strategy using a D-dimer threshold of 1000 ng/mL for patients where PE is not the most likely diagnosis is both safe and efficient. By reducing the reliance on chest imaging by 19%, this approach addresses the dual goals of modern healthcare: improving patient safety by avoiding over-diagnosis and over-treatment, while optimizing the use of hospital resources.
For clinicians, the takeaway is clear: the integration of clinical judgment with specific D-dimer thresholds is more effective than a “one size fits all” approach. As health systems continue to seek ways to streamline emergency care, this simplified “one-question” strategy offers a practical, evidence-based solution.
Funding and Clinical Trial Information
This study was funded by the Assistance Publique-Hôpitaux de Paris (Délégation à la Recherche Clinique et à l’Innovation). It is registered with ClinicalTrials.gov under the identifier NCT06190392.
References
1. Roussel M, Bannelier H, Lebal S, et al. D-Dimer thresholds for diagnosis of pulmonary embolism based on a single question: is it the most likely diagnosis? A prospective, multicentre, open-label, single-arm interventional study. Lancet Respir Med. 2026;14(1):29-37.
2. van der Hulle T, Cheung WY, Kooij S, et al. Simplified diagnostic management of suspected pulmonary embolism (the YEARS study): a prospective, multicentre, cohort study. Lancet. 2017;390(10091):289-297.
3. Righini M, Van Es J, Den Exter PL, et al. Age-adjusted D-dimer cutoff levels to rule out pulmonary embolism: the ADJUST-PE study. JAMA. 2014;311(11):1117-1124.
