Background Patients with mild traumatic brain injury (TBI) will receive a brain CT scan based on risk of injury. A previous study established a scoring system for patients with mild TBI that assigned <3 points for the low-risk group, 3–6 points for the moderate-risk group, and ≥6 points for the high-risk group. The purpose of this study was to evaluate the external validity of mild TBI risk scores for predicting intracranial hemorrhage in patients with mild TBI who had been transferred to receive a brain CT scan at the 10 nationwide CT scan–capable facilities in Thailand.

Methods The study was a retrospective cross-sectional review of patients with mild TBI who received a brain CT scan in 10 nationwide hospitals of Thailand. Risk factors were observed and points calculated for predicting mild TBI scores based on patient records. Injured patients were divided into two groups: CT scans indicating normal and abnormal brain images. After this, the accuracy of mild TBI score for predicting the presence of intracranial hemorrhage was investigated.

Results The study included a total of 999 patients, comprising 461 (46.15%) patients with abnormal brain CT scans indicating intracranial hemorrhage and 538 (53.85%) indicating no intracranial hemorrhage. In the low-risk group (mild TBI risk score <3), moderate-risk group (mild TBI risk score 3–6), and high-risk group (mild TBI risk score >6), the likelihood ratio positive of brain CT scans were 0.41, 3.53, and 77.3, respectively.

Discussion Mild TBI risk score may assist healthcare providers to select patients with mild TBI for brain CT scan referral, particularly in hospitals without CT scan facilities. In such cases, based on the proposed scoring system, immediate transfer of moderate-risk and high-risk patients with mild TBI to a CT scan–capable facility is necessary.