Abstract
Background Traumatic brain injury (TBI) is a global public health issue responsible for significant morbidity and mortality. TBI incorporates mild injuries such as concussion or more severe intracranial injuries such as bleeding and swelling of the brain. Many patients who sustain a significant head injury present to emergency departments (ED) for assessment. ED physicians must determine who requires a computed tomography (CT) head scan to rule out intracranial injuries, a decision with inherent challenges. To aid decision making and curtail the rapid increases in the rates of CT head use in ED, clinical decision rules (CDRs) have been introduced. Despite this, rates of CT head use are rapidly increasing, contributing to the resource pressures, and crowding facing EDs. Clinical biomarkers could be used to rule out intracranial injuries in patients with significant head injuries. Potentially, biomarkers could be incorporated into CDRs and reduce the rates of CT head use and ED length of stay in those without intracranial injuries, whilst ensuring those with intracranial injuries receive appropriate intervention in a timelier manner.
Section 1
Aim To describe how CT head scans are currently used in New Zealand (NZ) EDs.
Methods This section consisted of four separate retrospective studies evaluating: the clinical characteristics of patients requiring CT head scans and the adherence to the National Institute of Clinical Care Excellence head injury guidelines (NICE HIG) for CT; the impact of alcohol on head injuries; the indications and findings of all ED CT head scans- particularly noting the impact of TBI on CT head use; and the impact of COVID 19 on CT head use for TBI.
Conclusion The use of CT head scans in patients presenting to ED with suspected TBI contributes significantly to ED and radiology workload. The NICE HIG works well as a CDR but despite near-optimal adherence rates, the yield of significant intracranial injuries is low. The clinical characteristics of patients requiring CT head scans following head injury and the rates of significant intracranial pathology found was similar to international literature. Concerningly, a quarter of patients included had consumed alcohol prior to sustaining their head injury. During the COVID-19 lockdown, the proportion of patients who had a CT head scan performed, and the yield of positive CT findings remained the same as the previous year, suggesting that both health-seeking behaviour and physician decision making were not significantly affected by the lockdown.
Section 2
Aim To review the current evidence on the use of biomarkers as rule out tests for intracranial injuries in adult patients presenting to ED with suspected TBI.
Methods A systematic review and meta-analysis was conducted to review the diagnostic accuracy of S100B, GFAP and UCH-L1 to rule out intracranial pathology seen on CT head scan in adult patients presenting with TBI.
Conclusions The overall quality of evidence regarding the diagnostic accuracy of single biomarkers was low. S100B was the only biomarker with a validated clinical platform, predetermined cut-off threshold and moderate quality evidence. Rigorous local data with more robust clinical outcome and economic impact data is required to support the incorporation of biomarkers into ED CT head CDRs.
Section 3
Aim To investigate whether the addition of biomarkers improves the performance of CDRs for CT head scanning in patients presenting to NZ EDs with suspected TBI.
Methods This section consisted of an initial pilot study and an expanded multi-centre observational study evaluating the diagnostic performance of S100B to rule out intracranial pathology in patients meeting NICE HIG criteria for CT head.
Conclusion S100B shows promise as a diagnostic test to rule out significant intracranial pathology in patients presenting to ED within 6-hours of head injury. If used in addition to the NICE HIG, theoretically CT head rates could be reduced by one third and one third of patients could be discharged from ED without a scan. Targeting the use of S100B to those patients under 65 years of age, with isolated head trauma, may provide the best balance between safety and resource benefits.
Section 4
Aim To explore the perspectives of senior emergency physicians on the inclusion of clinical biomarkers in CDRs for CT head scanning in patients with suspected TBI.
Methods This was a descriptive qualitative study using 11 individual senior ED physician interviews to generate data. Thematic analysis of transcribed interviews was performed.
Conclusion The potential inclusion of biomarkers in CT head guidelines were viewed favourably by senior ED physicians, particularly with regards to decision support in low-risk head injuries. However, the lack of expert consensus or strong evidence demonstrating high diagnostic precision in comparable emergency care models limits their introduction.
Overall conclusions
This thesis demonstrates that CT head use for suspected TBI has a considerable impact on ED workload, yet the yield of significant injuries is low. Incorporating biomarkers into CDRs for low-risk patients could optimise risk stratification and reduce CT head request rates in this cohort. New clinical pathways and CDRs that incorporate biomarkers will need to be introduced cautiously and be supported by a strong evidence base. This will ensure ED physicians confidence and shift culture away from routine CT head use. Ultimately, this could alleviate some of the resource pressures and crowding that currently burden EDs in NZ and enable timely intervention for more serious intracranial injuries.