Plasma biomarkers are emerging as a vital diagnostic tool for mild traumatic brain injury (TBI) in older adults, a demographic where symptoms often overlap with preexisting cognitive decline or polypharmacy. A recent cross-sectional study of 89 adults aged 60 to 84 demonstrates that objective blood-based measures can clarify diagnoses when standard imaging and clinical presentations remain ambiguous.
Researchers evaluated four specific plasma biomarkers: glial fibrillary acidic protein (GFAP), ubiquitin C terminal hydrolase L1, brain-derived tau, and neurofilament light. All four markers were significantly elevated in patients with diagnosed mild TBI compared to healthy controls. GFAP demonstrated the strongest diagnostic performance, achieving an area under the curve of 0.93 after adjusting for age and sex. This indicates excellent accuracy, even in cases where CT scans showed no radiographic abnormalities.
Crucially, the study found that fixed biomarker thresholds are insufficient for this population. Optimal levels varied significantly by age and sex. For instance, GFAP thresholds rose from approximately 94 pg/mL at age 60 to over 200 pg/mL at age 84. Similarly, neurofilament light thresholds more than doubled across the same age range. Ubiquitin C terminal hydrolase L1 also displayed distinct sex-based differences, requiring higher cutoffs for females.
When personalized, age-and-sex-adjusted cutoffs were applied to patients with suspected but unconfirmed TBI, 67% exceeded the GFAP threshold and 89% exceeded the brain-derived tau threshold. This provides objective evidence of injury in clinically uncertain cases. While the study is limited by its small sample size and single-center design, it underscores the necessity of personalized thresholds to reduce diagnostic uncertainty in emergency settings.