SRS36 - External validation of the Liverpool Head Injury Tomography score (HIT Score)

Abstract Introduction Mild Traumatic Brain Injury (mTBI), defined as any TBI presenting with a GCS ≥ 13, is a common presentation globally. mTBI is commonly referred to Neurosurgery despite the absence of surgically significant injury. The Liverpool HIT score aimed to determine surgically significant injury by examining the presenting CT scan. The present study aims to externally assess the Liverpool HIT score for use as a screening tool in emergency and neurosurgical departments. Methods Data was collected for all referrals of mTBI to a regional tertiary neurosurgical centre between July-2019 and July-2021. The Liverpool HIT score was retrospectively calculated from the presenting scans by a team of 10 radiologists. The outcome was Neurosurgically-directed admission to Neurosurgery within 30 days of referral. The sensitivity, specificity and Negative Predictive Value(NPV) were calculated to assess clinical utility as a screening tool. Results Data for 2210 patients presenting with mTBI was collected from 9 referring hospitals in Yorkshire and the Humber to Leeds Centre for Neurosciences. The median age was 75 (IQR:53–87). 1330 (60.2%) presented with extra-axial haemorrhage, 761(34.4%) with subarachnoid haemorrhage,652(29.5%) with parenchymal injury and 518(23.4%) with skull fractures. 255(11.5%) had no scorable pathology. Overral,1402 (63.4%) had a HIT score of ≥3. The median HIT score was 3(IQR:1–4,Range:0–19). The sensitivity was 95.3,specificity was 41.6% and the NPV was 98.3%. Conclusions The Liverpool HIT score is a practical and effective screening tool for recognising surgically significant injury requiring Neurosurgical input, and can be used to screen mild TBI at presentation.