Can we reduce CT pulmonary angiography in the ER? A pilot calibrated scale for pulmonary embolism rule-out

Introduction Pulmonary embolism (PE) is the third most common cardiovascular disease and is associated with high mortality if left untreated. In large emergency departments (ERs), extensive use of computed tomography pulmonary angiography (CTPA) may lead to significant delays in patient flow and overcrowding. Purpose Our aim was to develop a pilot calibrated clinical-laboratory scale for PE rule-out in the ER. Methods We developed a pilot calibrated scale with scores ranging from 0 (lowest risk) to 7 points (highest risk) including seven clinical and laboratory variables (C-reactive protein-CRP, prothrombin time, international normalized ratio-INR, activated partial thromboplastin time-APTT, fibrin degradation products-D-dimers, systolic blood pressure-SBP, and oxygen saturation-Sp02). Patients with suspected PE representing to a single-center ER were retrospectively analyzed. Demographic, clinical, laboratory, and CTPA data were collected. Patients were classified as PE or non-PE based on CTPA results, and multivariate logistic regression was used to evaluate the association between scale score and PE diagnosis. Results In this single-center retrospective study 110 patients were enrolled, with mean age 67±15 years. PE was confirmed by CTPA in 21 patients (19%), while 89 patients (81%) constituted the non-PE group. Scale scores were strongly associated with PE diagnosis (p=0.001). Notably, no patient with a low scale score (<2) was diagnosed with PE, indicating effective rule-out in this subgroup. In contrast, nearly half of patients with high scores (≥5) had confirmed PE. For each of the PE-escalation categories, the statistically significant level of PE was approximately 7-fold higher in patients with suspected PE symptoms, weighted be the other factors in the model [OR=6.88, 95% CI: 2.17-21.85, p=0.001]. Conclusion This pilot calibrated scale demonstrates promising performance for PE risk stratification and early rule-out in the ER. These findings are consisted with current ESC guidelines, which emphasize rule-out strategies to reduce unnecessary CTPA in suspected PE. However, further validation in larger prospective studies is necessary.