Objectives & Background NICE guidelines are used to triage the 1.4 million patients attending the ED with head injury in England and Wales annually for CT imaging. These guidelines are based on research conducted in populations presenting within 24 hours of injury. We therefore postulated that they might not apply to those presenting later in the same way.

Objectives:

• 1) Estimate the proportion of CT head scans requested for patients presenting more than 24 hours after injury.

• 2) Compare the CT abnormality rate within and after 24 hours of injury.

• 3) Compare the use of the NICE guidelines and their sensitivity for intracranial injury within and after 24 hours.

Methods We reviewed ED trauma CT head requests from Hull Royal Infirmary for 6 months from Nov 2011. Requests were matched to ED records where possible. Correlation between the presence of a NICE indication and traumatic intra-cranial injuries was assessed (Pearson Chi-square test- SPSS 22).

Results 676 scans were performed for adult head trauma. 8.6% showed a traumatic abnormality; 1.2% required neurosurgery and 0.3% died. 650 records were available. The proportion of CT head scans completed for head injury patients presenting after 24 hours of injury was 15.5% (12.7–18.3% (95% CI). The CT abnormality rate was 8.4% (6.1–10.7% 95 CI) within and 9.9% (4.1–15.7% 95% CI) after 24 hours. 13.7% of CT scans within 24 hours and 38.6% of CT scans after were completed in patients with no NICE indication. Within 24 hours, NICE guidelines predicted 45/46 intracranial injuries (97.8% sensitivity [87–99.9% 95% CI]) and 7/10 injuries after (Sensitivity 70% [35.4–91.9% 95% CI]). The correlation between NICE indication and CT head abnormality for patients presenting within 24 hours (Chi-Square P=0.018) was not found in those presenting later (Chi-Square P=0.556).

Conclusion 15.5% (12.7–18.3% (95% CI) of scanned patients presented after 24 hours. The abnormality rate was similar to that found in those presenting earlier. NICE guidelines were less predictive in this group. A different approach for such patients may be required.