Aim: To assess the amount of computed tomography (CT) scans for minor head injury (MHI) performed in young patients in our emergency department (ED), not indicated by National Institute for Health and Clinical Excellence (NICE) and Canadian Computed Tomography Head Rules (CCHR), and to analyze factors contributing to unnecessary examinations. Secondary objectives were to calculate the effective dose, to establish the number of positive CT and to analyze which of the risk factors are correlated with positivity at CT; finally, to calculate sensitivity and specificity of NICE and CCHR in our population.
Materials and methods: We retrospectively evaluated 493 CT scans of patients aged 18-45 years, collecting the following parameters from ED medical records: patient demographics, risk factors indicating the need of brain imaging, trauma mechanism, specialty and seniority of the referring physician. For each CT, the effective dose and the negativity/positivity were assessed.
Results: 357/493 (72%) and 347/493 (70%) examinations were not in line with the CCHR and NICE guidelines, respectively. No statistically significant difference between physician specialty (p = 0.29 for CCHR; p = 0.24 for NICE), nor between physician seniority and the amount of inappropriate examinations (p = 0.93 for CCHR, p = 0.97 for NICE) was found but CT scans requested by ED physicians were less inappropriate [p = 0.28, odds ratio (OR) 0.562, CI (95%) 0.336-0.939]. There was no statistically significant correlation between patient age and over-referral (p = 0.74 for NICE, p = 0.93 for CCHR). According to NICE, low speed motor vehicle accident (p = 0.009), motor vehicle accident with high energy impact (p < 0.01) and domestic injuries (p = 0.002) were associated with a higher rate of unwarranted CT; according to CCHR only motor vehicle accident with high energy impact showed a significant correlation with unwarranted CT scan (p < 0.001, OR 44.650, CI 33.123-1469.854). 2% of CT was positive. Multivariate analysis demonstrated that factors significantly associated with CT scan positivity included signs of suspected skull fracture (p < 0.001, OR 20.430, CI 2.727-153.052) and motor vehicle accident with high energy impact (p < 0.001, OR 220.650, CI 33.123-1469.854). In our series, CCHR showed sensitivity of 100%, specificity of 74%; NICE showed sensitivity of 100%, specificity of 72%.
Conclusion: We observed an important overuse of head CT scans in MHI; the main promoting factor for inappropriate was injury mechanism. 2% of head CT were positive, correlating with signs of suspected skull fracture and motor vehicle accident with high energy impact.
Keywords: CT overuse; Clinical decision rules; Computed tomography; Emergency department; Head CT; Minor head injury.