Prevalence of negative CT scans in a level one trauma center

Purpose: The rise of computed tomography (CT) use in trauma has become the subject of concern given the harms of CT including radiation, cost, over diagnosis and identification of incidental lesions. We developed a novel metric, the Negative CT Score, (∑_CT−) which quantifies how often CT imaging identifies important injuries. Our objective was to describe the pattern of CT utilization in trauma at an urban academic level one trauma center using this novel metric. Methods: This was a retrospective study of intermediate level trauma patients who received CT imaging over a 1-year study period at an urban level one trauma center. We applied the Negative CT Score, (∑_CT−) to quantify the results of CT imaging. ∑_CT− is computed by subtracting the number of non-extremity body regions (maximum four: head, neck, chest, abdomen) with an important positive CT finding (defined by a priori criteria) from the total number of non-extremity body regions scanned. Results: Of the 552 cases reviewed during the study period, 410 (74.3%) were male and the mean age was 40.3 years [SD ± 21.2]. Four hundred eighty-six patients (88.0%) suffered blunt trauma; 66 (12.0%) suffered penetrating trauma. The average injury severity score for admitted patients was seven. Four hundred ninety-five cases had at least one CT performed. The average number of regions per patient that received CT imaging was 2.36 (SD ± 1.3), and the average ∑_CT− was 2.10 (SD ± 1.2). Three hundred and sixty-seven (74.3%) patients had no important findings on CT imaging. Conclusions: In a consecutive series of 552 intermediate trauma patients at our urban trauma center, 2.36 body regions were scanned per patient; of these, 2.10 regions revealed no important CT findings. We hope that these results and the Negative CT Score can be used to identify trends, variations in practice, and outliers within and across departments so that CT utilization can be optimized.