The U.S. Centers for Disease Control and Prevention (CDC) estimates that 1.7 million people in the United States sustain a traumatic brain injury (TBI) each year. Furthermore, TBI is a contributing factor to about one-third of all injury-related deaths in the United States and is a leading cause of death and disability in people under age 45, with an estimated 138 people dying from TBI each day. Those who survive often withstand effects that can last from a few days to the rest of their life. These symptoms can include impaired memory, depression, mood swings, and loss of sensations (like hearing and vision).
Part of the problem has been that TBIs, particularly mild traumatic brain injuries (mTBI) and concussions, have been difficult to concretely diagnose. Tests have traditionally been subjective, providing non-conclusive results. Furthermore, symptoms do not always present after a person suffers a brain injury. When they do, they often present slowly and can come in a variety of forms, making it difficult for medical professionals to diagnose them. Accurate diagnoses often require an extensive series of tests, such as examining a patient’s functional abilities, cognitive skills, and memory changes, among others, which can be time-consuming and still ultimately subjective. Today’s diagnostic protocol also typically includes several brain scans, including MRIs, which can be invasive and costly.
Despite the difficulty of diagnosing TBIs, letting brain injuries go undiagnosed can be exceedingly detrimental, as repeated trauma to the head can perpetuate the damage, increasing the chance of death and the probability of developing serious neurodegenerative disorders such as chronic traumatic encephalopathy (CTE).
The search for biomarkers
The absence of validated biomarkers in the neurology field is a major factor that has limited our understanding of the natural history and long-term effects of TBI, as well as our ability to develop a conclusive test for the diagnosis of TBI, and has been a major barrier to drug development in this area. Over the past few years, however, there has been significant progress in the identification and reliability of biomarkers indicative of brain injuries. Glial fibrillary acid protein (GFAP), ubiquitin c-terminal hydrolase L1 (UCH-L1), as well as other proteins, including microtubule-associated protein tau, amyloid beta peptide (Aβ42), and neurofilament light (NfL), have been proposed as promising diagnostic and prognostic biomarkers in TBI.
Despite the progress made with the identification of these biomarkers for brain injury, until now, current assays have not been sensitive enough to reliably detect levels of several key neurological biomarkers in plasma. When injury occurs to the brain, proteins are released in minute concentrations; they travel across the blood-brain barrier and into the bloodstream. It was previously thought that the blood-brain barrier prevented these telltale proteins from entering circulation; however, new research and technological advancements have proven this to be false, highlighting the promise that lies in a blood test for brain injury.
Still, traditional laboratory tools and tests have lacked the specificity and precision needed to create assays sensitive enough to accurately detect and measure biomarkers for TBI. As technology progresses, though, researchers are beginning to develop assays critical for the measurement and quantification of biomarkers indicative of brain injury. This ultra-sensitive, single-molecule technology is able to not only detect biomarkers indicative of brain injury but also quantify them, at the most minute levels.
The laboratory’s role in the development and validation of these highly sensitive immunoassays has been critical. For instance, the assays for GFAP and UCH-L1, with an achievement of sub-pg/mL, were both developed in a dedicated research lab created for the development and testing of assays critical in the evaluation of disease biomarkers. Researchers were able to measure biomarkers with great sensitivity to create assays and test hypotheses.
In the creation of assays GFAP and UCH-L1 specifically, the scientists were able to fully characterize and validate the assays for performance, including lower limits of quantitation (LOQ), linear range of calibration, spike recovery, and dilutional linearity. Using each of the optimized assays, a total of 90 clinical samples from three different diagnostic groups (normal, mild-moderate TBI, and severe TBI) were analyzed for both biomarkers. While these evaluated samples showed both proteins to be useful potential TBI biomarkers, GFAP exhibited a better statistically significant separation than UCH-L1 between normal and TBI samples.
Technology has also been used to test for other biomarkers indicative of neurological injuries, including tau, Aβ42 and NfL. For example, in a study of military personnel who sustained a TBI while being deployed, researchers found that concentrations of plasma tau were significantly elevated in the 70 participants with self-reported TBI compared with the 28 controls.1 In a separate study evaluating NfL,2 researchers found baseline mean plasma NfL levels were elevated in patients with progressive supranuclear palsy (PSP) and could therefore be of value as a biomarker both to assist clinical diagnosis and to monitor pharmacodynamic effects on the neurodegenerative process in clinical trials. Further, in a recent study of TBI subjects enrolled in a Citicoline Brain Injury Treatment Trial,3 it was demonstrated that, in samples collected shortly after a suspected concussion (day 0), as well as at days 30 and 90, GFAP, Aβ42, and tau were all significantly elevated soon after injury (day 0) and were excellent biomarkers for the discrimination of complicated mTBI cases from controls.
Looking forward to clinical use
The development of highly sensitive immunoassays for GFAP, UCH-L1, tau, NfL and Aβ42 have all been critical in advancing our understanding of the effects of TBIs, bringing us one step closer to a definitive diagnostic test that could one day be used to objectively test for brain injuries, even when symptoms are not overtly present. With the U.S. Food and Drug Administration’s (FDAs) recent approval of two medical devices that have the ability to detect changes in cognitive skills often associated with brain trauma, there is evidence that healthcare organizations, as well as the public, are eager for the development of these tests.
While more research is needed before this can happen, we believe that the progress that has been made in the development of assays for biomarkers indicative of brain injuries will encourage the creation of point-of-care devices and eventually improve treatment options for patients. The collaboration of researchers and scientists from across vendors and organizations is expected to play a vital role in the continued advancement of these tests. Laboratories that allow for this type of partnership and experimentation will play a critical role in the enabling of early disease detection in neurology and other therapeutic areas.
- Olivera A, Leibman N, Jeromin A, et al. Peripheral total tau in military personnel who sustain traumatic brain injuries during deployment. JAMA Neurol. 2015;72(10):1109-16.
- Rojas JC, Karydas A, Bang J, et al. Plasma neurofilament light chain predicts progression in progressive supranuclear palsy. Ann Clin Transl Neurol. 2016;3(3): 216–225.
- Bogoslovsky T, Wilson D, Chen Y, et al. Increases of plasma levels of glial fibrillary acidic protein, tau, and amyloid ß up to 90 days after traumatic brain injury. J Neurotrauma. 2017;34(1):66-73.
David Hanlon, PhD, serves as Sr. Director, Business Development and Strategic Collaborations, for Massachusetts-based Quanterix Corporation.
NIH-funded research suggests need for new treatment strategies to help veterans recover
According to a new study in JAMA Neurology, U.S. military service members who endured a mild concussion after blast injury while deployed in Iraq or Afghanistan may continue to experience mental health symptoms as well as decreases in quality of life for at least five years after their injury. The study was supported by the National Institute of Neurological Disorders and Stroke (NINDS) and the Department of Defense. NINDS is part of the National Institutes of Health (NIH).
“This is one of the first studies to connect the dots from injury to longer-term outcomes and it shows that even mild concussions can lead to long-term impairment and continued decline in satisfaction with life,” said lead author Christine L. Mac Donald, PhD, an associate professor in the Department of Neurological Surgery at the University of Washington School of Medicine in Seattle. “Most physicians believe that patients will stabilize 6-12 months post-injury, but this study challenges that, showing progression of post-concussive symptoms well after this time frame.”
Dr. Mac Donald’s team studied five-year outcomes in 50 service members who experienced mild traumatic brain injury (mTBI) in Iraq or Afghanistan and compared the findings to 44 controls who were deployed but not injured. The researchers have been studying the service members with mTBI since their injury and examined changes in their symptoms from one year to five years after injury. The service members underwent a battery of neurological and neuropsychological assessments as well as tests of their overall functional ability to return to work and live independently.
The study also showed that a combination of factors, including neurobehavioral symptom severity, walking ability, and verbal fluency at one year after injury, was highly predictive of poor outcomes five years later.
“We need to identify effective, long-term treatment strategies that will help these brave men and women enjoy the highest quality of life possible following their service to our country,” said Walter Koroshetz, MD, director of NINDS. “This unique academic-military partnership highlights the power of data sharing and cutting across traditional boundaries to advance research that will help improve the lives of our military members.”
Blast injury due to improvised explosive devices was the representative injury of the wars in Iraq and Afghanistan. Approximately 20 percent of deployed service members in Iraq and Afghanistan experienced head injury. While the majority of those injuries were considered mild, the long-term effects are unknown.
Mac Donald’s group also found that while 80 percent of service members with concussions had sought treatment from mental health providers, only 19 percent reported that those programs were helpful. The authors note that this suggests the need for more targeted treatment options with longer-lasting benefits.
Mac Donald and her colleagues are currently examining a larger group of service members in order to validate these findings and are looking at how injured service members are doing
beyond five years.
This work was supported by the NINDS (NS091618-01) and the Department of Defense (W81XWH-13-2-0095).
The NINDS is the nation’s leading funder of research on the brain and nervous system. The mission of NINDS is to seek fundamental knowledge about the brain and nervous system and to use that knowledge to reduce the burden of neurological disease.