Cost effectiveness of imaging strategies in the emergency department for the diagnostic workup of community-acquired pneumonia: a real-life retrospective study

Background The purpose of this study was to compare the length of stay (LOS) and costs of diagnostic workup by Ultra Low Dose (ULD) chest computed tomography and radiography for patients treated for a community-acquired pneumonia (CAP) in the emergency department (ED). Methods We conducted a real-life retrospective study of patients treated for a CAP in two ED between March 1, 2019 and February 29, 2020. We estimated length of stay (LOS) as the difference between ED discharge and entry times, total hospital costs at 60 days including ED, initial admissions and readmissions. Patients with initial radiography were compared with patients with initial ULD CT using inverse probability weighing of the propensity score calculated from demographic variables, vital parameters and clinical presentation. We calculated the incremental cost effectiveness ratio as the difference between costs and the difference between LOS. Variability of the results was assessed using non-parametric bootstrapping. Results We included 1609 consecutive patients, 1476 patients with radiography and 133 patients with ULD CT. The average costs were respectively €4317 [3483; 5067] and €4223 [4034; 4612] with 11.9 [10.1; 13.2] and 11.7 [11.5; 12.2] hours of LOS in the ED for chest radiography and ULD chest CT respectively, resulting in lower costs of € -94 [-870; 819] and a decreased LOS of 12 [-108; 76.9] minutes in favor of ULD chest CT. Conclusions In this real-life study, the management of CAP in ED by ULD chest CT compared with chest radiography resulted in lower costs without increasing LOS. Trial registration This study was registered with the Clinical Trials Registry (NCT05140408).