Analysis of the Positivity Rate of Sector-based Whole-body CT Scans in Grade C Trauma Patients in Essonne

Grade C trauma patients are a diagnostic and logistical challenge: their initial presentation is reassuring, yet the mechanism of injury may conceal severe lesions, which is why whole-body CT is recommended as first-line imaging6. The destination chosen at the pre-hospital stage therefore determines both the speed of diagnosis and the speed of access to specialized care. In Essonne, where no level 1 trauma center exists, this choice is made by the SAMU dispatch physician, case by case, without local data on how often a scan performed at the sector hospital reveals lesions requiring specialized management. The delays reported after an abnormal local scan are the main argument for direct transfer, while the unnecessary mobilization of resources and the transport of patients who turn out to have normal scans are the main argument against.

This is a retrospective, multicenter, observational cohort study. It covers hospitals of the Essonne department that received grade C trauma patients managed by an Essonne SMUR team in 2025 and who received a whole-body CT. Cases will be identified from SMUR and SAMU activity records, then linked to the receiving hospitals' medical files. No intervention will be performed and no change to patient care is planned.

Data will be extracted from SAMU dispatch records, emergency department files and radiology reports. Variables will include:

• demographics and relevant medical history
• mechanism of injury and pre-hospital clinical findings
• time stamps for each care step (SMUR arrival on scene, hospital arrival, scan, specialist consultation, secondary transport, arrival at final destination)
• whole-body CT findings
• the level of care needed (local hospital, level 2 or level 1 trauma center)
• secondary transfers, and the regulation time required for them

Data will be recorded in a pseudonymized, secure database. Descriptive statistics will be used for the whole cohort. The proportion of abnormal whole-body CT scans will be reported with its 95% confidence interval.

Adult (\>18 years) grade C trauma patients attended on scene by an Essonne SMUR team between 01/01/2025 and 31/12/2025, who underwent a whole-body CT scan at the sector hospital. A grade C patient is stable (no hemodynamic disorder) and meets no grade A or B criterion, but has a high-risk mechanism of injury (fall of more than 6 m, ejected, crushed, thrown or blasted victim, death of a passenger in the same vehicle, proximal open limb fracture or closed fracture of at least 2 long bones) and/or an at-risk medical background.

Diagnostic Test: Whole-body CT scan at the sector hospital

Whole-body computed tomography performed as first-line imaging in the radiology department of the sector hospital covering the accident site, as part of routine care. Its results (trauma-related lesions, level of care required, secondary transfer to a trauma center) are analysed retrospectively.

Time frame: at day 0

A whole-body CT scan is considered pathological if it shows trauma-related lesions on imaging, whatever their severity. Lesions discovered incidentally or present before the accident are not counted. Data are collected from the Essonne SAMU dispatch software and, for missing data, by calling the receiving emergency departments of the sector hospitals.

Time frame: at day 0

Final orientation of patients with a pathological whole-body CT scan, analysed qualitatively: proportion of patients secondarily transferred to a level 1 trauma center or an intensive care unit, and distribution between patients who can be managed at the sector hospital and those requiring care in a level 1 or level 2 trauma center.

Time frame: at day 0

Total duration between the initial SMUR care and the arrival of the patient at the final destination, used to evaluate the impact of under-triage of grade C trauma patients by comparison of delays (Wilcoxon test). Delays are described as medians with interquartile ranges.

Time frame: at day 0

Descriptive analysis of the cohort of grade C trauma patients: proportion of pathological scans according to age, sex, medical background, type of accident and the criterion defining grade C.

Analysis of the Positivity Rate of Sector-based Whole-body CT Scans in Grade C Trauma Patients in Essonne