A NEW prospective study suggests that a simplified D-dimer strategy can safely rule out pulmonary embolism in the emergency department while substantially reducing the need for chest imaging. By combining a 1000 ng/mL threshold for low-likelihood patients with an age-adjusted threshold for others, clinicians may streamline diagnostic pathways without compromising safety.
Pulmonary embolism remains a challenging diagnosis in emergency settings, with overuse of imaging contributing to costs, delays, and patient exposure to radiation. Traditional validated strategies allow D-dimer thresholds to be raised in selected low-risk patients, but adherence is often poor. This study tested a pragmatic approach using a single clinical question, whether pulmonary embolism is the most likely diagnosis, to guide threshold selection.
Low Failure Rates Across Patient Groups
The trial enrolled 1,221 adults presenting with suspected pulmonary embolism across 13 French emergency departments. Patients not receiving full-dose anticoagulation and without recent thromboembolic events were included. Among 997 patients for whom pulmonary embolism was not considered the most likely diagnosis, applying a 1000 ng/mL D-dimer threshold yielded a diagnostic failure rate of 0.00% (95% CI: 0.00–0.34), well below the predefined safety limit. Even after accounting for missing follow-up, the failure rate remained extremely low at 0.12%.
In a prespecified subgroup of 796 patients who had pulmonary embolism ruled out without chest imaging, no thromboembolic events occurred during 3 months of follow-up. These findings demonstrate that the simplified strategy maintains safety while potentially avoiding unnecessary investigations.
Reduced Reliance on Chest Imaging
Overall, only 32% of patients underwent chest imaging under the simplified approach, compared with 50% using a standard 500 ng/mL D-dimer threshold. This represents an absolute reduction of 19%, highlighting a meaningful opportunity to streamline emergency department workflows and minimise patient exposure to radiation.
Implications for Emergency Care
By combining a straightforward clinical assessment with tailored D-dimer thresholds, this strategy allows safe, efficient exclusion of pulmonary embolism. While additional studies could explore wider implementation, the findings indicate that using a 1000 ng/mL threshold in low-likelihood patients can reduce imaging demand without compromising diagnostic safety, offering a practical tool for emergency clinicians.
Reference
Roussel M 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.
