External validation of the Liverpool Head Injury Tomography Score for mild traumatic brain injury

Background Mild Traumatic Brain Injury (mTBI) neurosurgical referrals are increasing. This study aimed to externally validate a radiological scoring system to define a ‘neurosurgically significant’ mild TBI and evaluate its impact on referral outcome if implemented. Method Retrospective, external validation of the UK Liverpool Head Injury Tomography Score (LIV-HITS). Consecutive neurosurgery referrals to a tertiary neurosurgery centre for mild TBI were included (1st January 2022—30th June 2022). Mechanism of injury, LIV-HITS and management decision were identified, and diagnostic accuracy determined. Results A total of 1547 referrals were included. 147 (9.5%) were accepted for transfer, and 1400 (90.5%) were designated as local management. For neurosurgical transfer, the sensitivity of LIV-HITS was 99.3% and the specificity was 43.9%, with a positive predictive value of 15.7%, and negative predictive value of 99.8%. Discriminatory power of the model was fair (AUC 0.71, 95% CI 0.66–0.76). In 6 months, the score identified 615 referrals (39.8%) that could have been successfully triaged to local management if the scoring system was used. Conclusions The LIV-HITS has a sensitivity of over 99% for excluding a neurosurgically significant mild TBI in an externally validated cohort. However, the discriminatory power of the score is poor for stratifying which patients eventually get transferred to a neurosurgical centre. The score in clinical practice could be used as a ‘rule out’ tool for mild TBI referrals, whilst identifying potentially significant mild TBI that would warrant emergency neurosurgical consideration.