February 19, 2020
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Blood test helps triage older patients with mild TBI

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A blood test that the FDA approved in 2018 for mild traumatic brain injury had the same sensitivity and negative predictive value in older patients as it did in younger patients, thus providing clinicians with what one researcher called a “valuable” triaging tool in a vulnerable population.

“Most patients with a minor head injury — mild TBI or concussion — are assessed and diagnosed based on overt symptoms and measures of consciousness,” Robert H. Christenson, PhD, DABCC, FACB, professor of pathology at the University of Maryland School of Medicine, told Healio Primary Care. “CT scans are often used as a secondary measure to evaluate and identify intracranial injuries that are difficult to diagnose based on symptoms alone. While CT is critically important in managing head injury patients, less than 10% of patients who undergo a head CT scan have actionable findings.”

Researchers conducted a post-hoc analysis of A Prospective Clinical Evaluation of Biomarkers of Traumatic Brain Injury (ALERT-TBI) study. ALERT-TBI was a multicenter study that validated the performance of the Brain Trauma Indicator blood test, which uses two biomarkers — ubiquitin carboxyl-terminal esterase L1 (UCH-L1) and glial fibrillary acid protein (GFAP) — to predict brain injuries within 12 hours of a suspected TBI.

“Realizing that many patients who are evaluated for possible TBI/concussion are elderly, we asked an age-centered question, and analyzed it using the study data that was submitted and ultimately led to the FDA approval of the Brain Trauma Indicator,” Christenson said.

The researchers assessed how age impacted UCH-L1 and GFAP values in 1,959 patients with TBI, 25.7% of whom were aged 65 years and older.

They found that the sensitivity and negative predictive value of GFAP/UCH-L1 were both 100% — meaning the blood test correctly predicted which older patients with concussion did not have brain tissue damage and did not need a CT scan.

However, the tests specificity was significantly lower in patients aged 65 years and older (0.131) vs. patients aged 65 years and younger (0.442), and the specificity decreased stepwise with older age. Compared with younger patients, older patients with mild TBI and without abnormal CT findings had a significantly higher GFAP (38.6 vs.16.2 pg/mL) and UCH-L1 (347.4 vs. 232.1 pg/mL) values.

Brain Trauma Indicator
Photo courtesy: Robert H. Christenson

“The data indicate that this lab test that measures GFAP and UCH-L1, which should be administered within 12 hours of the head injury, provides considerable opportunity to improve patient management by aiding in medical decision-making, and develop a more comprehensive profile of their patient’s health,” Christenson explained. “Primary care and emergency physicians may employ the test in their practice to help differentiate between those patients that will benefit from advanced medical imaging and those that do not and to mitigate the disadvantages and cost of advanced imaging.”

According to Christenson, the Brain Trauma Indicator is a little bigger than, and weighs about two times more than, an iPhone and takes 10 minutes to provide results once the patient’s blood sample is placed in the device. Conversely, another means of knowing if advanced medical imaging is necessary — taking the blood sample, sending the sample to the lab, testing the sample and getting results, those results entered into the lab’s information system, centrifuging the sample, running the test again and releasing the results to the patient’s clinician — can be much more time-consuming.

Christenson also mentioned that the developer of the Brain Trauma Indicator, Banyan Biomarkers, is working with health care providers to make the device routinely available in labs and in the point of care.

According to a press release, the EyeBOX concussion test that the FDA authorized last year that uses eye-tracking to confirm concussions was not specifically designed for older patients, suggesting another possible reason to use Christenson and colleagues’ technique. – by Janel Miller

References:

Clinical Trials. Prospective Clinical Evaluation of Biomarkers of Traumatic Brain Injury (ALERT-TBI) study. https://clinicaltrials.gov/ct2/show/NCT01426919. Accessed Feb. 7, 2020.

Ward MD, et al. J Appl Lab Med. 2020;doi:10.1093/jalm.2019.031393.

Disclosures: Christenson reports professional relationships with the American College of Cardiology, Roche Diagnostic Systems, Siemens Healthineers and The Journal of Applied Laboratory Medicine. Please see the study for all other authors’ relevant financial disclosures.