New blood test can help identify elderly concussion patients with brain tissue damage

Novel research shows that a blood test can differentiate elderly concussion patients with brain tissue damage from those without it. This finding, published in the special brain health collection of AACC's The Journal of Applied Laboratory Medicine, could help ensure that elderly patients with severe concussions receive crucial treatment for their injuries.

Traumatic brain injury is a significant health concern among the elderly, with adults age 75 or older experiencing rates of traumatic brain injury-related hospitalization and death that are higher than any other age group. Most traumatic brain injuries that the elderly incur are concussions, which can cause intracranial bleeding (i.e. bleeding within the skull) that must be treated immediately. Diagnosing intracranial bleeding in the elderly comes with numerous challenges, though. The American College of Emergency Physicians recommends that all elderly concussion patients undergo computed tomography (CT) scans to check for intracranial bleeding, because issues such as age-related cognitive decline or dementia can mask signs of bleeding-induced mental impairment. However, CT scans are very expensive and expose patients to radiation, and both the healthcare system and patients would benefit from reduced CT scan use.

Recently, the Food and Drug Administration authorized a blood test that identifies head injury patients who have brain tissue damage that needs to be assessed via CT scan. This blood test was not specifically designed for elderly patients, though, so a team of researchers led by Robert H. Christenson, PhD, of the University of Maryland School of Medicine in Baltimore, set out to determine how well the test performs in patients age 65 years or older. To do this, Christenson's team retrospectively analyzed data from the Prospective Clinical Evaluation of Biomarkers of Traumatic Brain Injury (ALERT-TBI) study. In this study, 1,959 adult patients with a concussion underwent both a CT scan and blood test for brain tissue damage within 12 hours of their injury. Christenson's team compared the results of the CT scan and blood test-;which measures the proteins glial fibrillary acidic protein (GFAP) and ubiquitin carboxyl-terminal esterase L1 (UCH-L1)-;in patients 65 years of age or older and in patients younger than 65.

From this comparison, the researchers found that the GFAP/UCH-L1 blood test predicts with 100% accuracy which elderly concussion patients do not have brain tissue damage and do not need a CT scan. Hospitals can therefore use this test to triage elderly concussion patients so that clinicians can focus on those most likely to require urgent intervention for intracranial bleeding. Importantly, however, the researchers also found that the test does not accurately identify elderly patients who do have brain tissue damage, which means that the test should only be used as a triage tool, not as a replacement for CT scans.

This post-hoc analysis of the ALERT-TBI study further validates the utility of the [mild traumatic brain injury] serum assay as a rule-out test across the spectrum of adult ages, based on equivalent sensitivity and negative predictive value. However, the identified differences in specificity and serum GFAP/UCH-L1 values in elderly [traumatic brain injury] patients limits use as a rule-in test, and highlights age-specific characteristics that must be considered in the use of the predictive markers in elderly [mild traumatic brain injury] patients.

Robert H. Christenson, PhD, of the University of Maryland School of Medicine in Baltimore