Biomarkers for acute mild brain injury (BAMBI): optimising GFAP/UCH-L1 thresholds to support CT stewardship in a NICE-guided mild-traumatic-brain-injury cohort.

BACKGROUND

NICE head injury guidance prioritises sensitivity but results in high CT utilisation and low diagnostic yield, contributing to Emergency Department (ED) crowding, particularly among older adults after falls. GFAP/UCH-L1 blood biomarkers may support safer CT stewardship, although limited specificity in older adults may reduce clinical impact.

OBJECTIVE

To evaluate plasma GFAP/UCH-L1 against CT findings in a Major Trauma Centre ED cohort and assess whether age-stratified interpretation improves clinical utility while preserving rule-out performance.

METHODS

Adults with suspected mild traumatic brain injury (mTBI:GCS 13-15) who underwent non-contrast head CT and had plasma GFAP/UCH-L1 measured within 12 hours of injury were included (n=215). Manufacturer thresholds (GFAP 35 pg/mL; UCH-L1 400 pg/mL; OR rule) were compared with an age-stratified algorithm (GFAP 115 pg/mL;UCH-L1 335 pg/mL;OR rule) applying higher published thresholds in participants ≥65 years.

RESULTS

Nineteen participants were CT-positive (8.8%). Manufacturer thresholds achieved 100% sensitivity and 29.6% specificity, with 27.0% biomarker-negative. Age-stratified interpretation preserved 100% sensitivity while improving specificity to 55.1% and increasing biomarker-negative results to 50.2%. In participants ≥65 years, specificity improved from 11.2% to 62.2%.

CONCLUSION

In this NICE-imaged ED cohort, GFAP/UCH-L1 showed strong CT rule-out performance. Age-stratified interpretation substantially improved specificity, supporting larger prospective validation and pathway evaluation.