Background
There are over 1.4 million annual attendances in the UK to Emergency Departments (EDs) following a head injury, and in 2010 2 .5 million people were treated for traumatic brain injury (TBI) in the United States. 95% of head injured patients present with an initial GCS of 13-15. In this group, around 7% of patients have brain injuries identified by CT imaging but only 1% of patients have life-threatening injuries.

It is unclear which injuries are clinically significant, so patients with brain injuries identified by CT imaging are admitted for monitoring. If risk could be accurately predicted admissions for low-risk patients could be avoided and resources could be focused on those with greater need.

Aims
1) Estimate the proportion of GCS13-15 patients with traumatic brain injury identified by CT imaging admitted to hospital who clinically deteriorate 
2) Develop a prognostic model highly sensitive to clinical deterioration which could help inform discharge decision making in the ED.

Methods
A retrospective case note review of 2000 patients with an initial GCS13-15 and traumatic brain injury identified by CT imaging is being completed at three English major trauma centres. The prevalence of clinically significant deterioration including death, neurosurgery, intubation, seizures or drop in GCS by more than 1 point will be estimated. Candidate prognostic factors have been identified in a previous systematic review. Multivariable logistic regression will be used to derive a prognostic model and its sensitivity and specificity to the outcome of deterioration will be explored.

Results
To date, data has been collected on 1515 patients: 66% were male, mean age 58 years, 10% were anti-coagulated, 19% were taking pre-injury anti-platelet medication, 57% presented with an initial GCS15, 32% presented with an initial GCS14, and 11% presented with an initial GCS13. 

26.5% of patients clinically deteriorated as a result of their TBI, 8% of patients underwent neurosurgery and 4% of patients died. 

The following were highly predictive of deterioration in uni-variable analysis: age, initial GCS, use of anti-coagulants, use of anti-platelets, abnormal neurological examination, size of intra-cranial injury and number of intra-cranial injuries. 

Discussion

Data collection is projected to finish in March 2019. The estimated rate of deterioration in the cohort was relatively high compared to previous studies but consistent with the older age and high rate of anti-coagulation of the study population. Analysis will now focus on developing a multivariable model which is highly sensitive to deterioration which could be used to risk stratify this population and inform further clinical management.

The development of a prediction model in Mild Traumatic Brain Injury with CT scan abnormality: preliminary findings of a multi-centre cohort study.