Limited clinical utility of risk stratification for CT decision-making in patients ≥ 75 years with mild traumatic brain injury.

BACKGROUND: Older adults account for an increasing proportion of emergency department visits for mild traumatic brain injury (mTBI). Although age is incorporated as a high-risk criterion in major clinical decision rules, the operational impact of risk stratification on computed tomography (CT) utilization in very elderly patients remains uncertain. METHODS: We conducted a retrospective cohort study including 3088 consecutive patients aged ≥ 14 years presenting with mTBI (Glasgow Coma Scale 13-15) between 2019 and 2022. The primary outcome was the presence of an acute intracranial lesion on head CT. Multivariable logistic regression models were developed to identify independent predictors. Model performance was assessed using optimism-corrected estimates of the area under the receiver operating characteristic curve (AUC), with 95% confidence intervals, after bootstrap internal validation. In patients aged ≥ 75 years, probability thresholds were selected to achieve predefined sensitivity targets (100% and 99%) to estimate potential reductions in CT utilization. RESULTS: CT was performed in 2657 patients (86.0%), identifying 155 acute intracranial lesions (5.8%). Patients aged ≥ 75 years represented 54.7% of the cohort and underwent CT in 98.2% of cases. In this subgroup, the prediction model showed moderate discrimination (optimism-corrected AUC 0.693; 95% CI, 0.610-0.775). At a threshold ensuring 100% sensitivity, CT utilization could be reduced by only 1.5% (specificity 1.6%). Allowing sensitivity to decrease to 99.0% increased potential CT reduction to 10.6% (specificity 11.2%). CONCLUSIONS: In patients aged ≥ 75 years with mTBI, multivariable risk stratification demonstrates moderate discrimination but minimal capacity to safely reduce CT imaging. High baseline risk and low tolerance for missed lesions substantially limit the operational benefit of rule-out strategies in this population.