Blood Tests for Brain Diseases
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Definitive diagnosis for many neurodegenerative diseases – such as Alzheimer’s, Parkinson’s, or Chronic Traumatic Encephalopathy (CTE) – frequently comes far too late. With dementia patients, doctors assess memory and behavior using specialized cognitive tests, though the results of these tests can be ambiguous. The “true gold standard” for diagnosis of both Alzheimer’s and CTE is through direct postmortem examination of brain tissue. Now, both researchers and athletes are working to change that.
Over the last fifteen years, positron emission tomography (PET) scans have been adapted to detect Alzheimer’s by checking for the buildup of sticky beta-amyloid plaques. These plaques are made of large clumps of protein that aggregate in the brain, inhibiting cell signals and triggering inflammation. PET scans frequently lead to changes in diagnosis for patients, but with a price tag upwards of $3,000 a scan, it can be years before a patient has one. PET scans for CTE and Parkinson’s are also in development, with the first case of CTE confirmed by autopsy last year. Recently, developments have been made that may usher in blood tests as diagnostic tools for these neurodegenerative disorders.
Researchers in Japan and Australia are developing a blood test to detect Alzheimer’s disease . Published January 31 in Nature, their study focuses on the detection of blood levels of Amyloid-β in the blood. Authors hypothesize that their test can predict the diagnosis of the disease possibly as much as 30 years before its onset. Although there is no cure for Alzheimer’s, the early warning would give patients time to cut back on sugar, get more sleep, or enroll in clinical trials at an earlier stage of the disease, which is more likely to be beneficial. That said, the test is still relatively early in development. The results were 90% accurate compared to PET scans, the diagnostic power of which is still considered controversial by some scientists. Additionally, different overall levels of Amyloid were seen between participants from the two countries, indicating that there is likely some optimization left to do. Although off to an exciting start, the test may not yet be ready for widespread use.
Separately, on February 14 the FDA approved marketing of a different blood test  to aid in evaluation of concussion. The test, named the “Banyan Brain Trauma Indicator,” works by detecting levels of GFAP and UCH-L1, two proteins associated with (though not necessarily limited to) traumatic brain injury. It has a 97.5% accuracy rating compared to expensive and irradiating CT scans, and results are available in 3-4 hours. While the prospect of making concussion diagnosis more affordable and widely available is exciting, identifying individuals such as athletes or soldiers who have suffered repeated brain trauma may indicate risk for CTE.
In addition, a new study was announced specifically to detect CTE in former NFL players this past week . CTE is a progressive neurodegenerative disease found in people who have suffered repeated traumatic impacts to the brain, particularly athletes who play contact sports. Last year, a Boston University team found evidence of CTE in the brains of 110 out of 111 retired football players. If the current study is fully enrolled, it will be the largest ever cohort of football players involved in a CTE study. Researchers at Exosome Sciences, Inc. will focus on developing 'TauSome' – a measurement of plasma extracellular Tau, or tiny droplets excreted by cells containing Tau protein – as a marker of CTE in blood and/or urine. This Institutional Review Board-approved work follows up on a preliminary study published in 2016 in which levels of TauSome were significantly higher in NFL players. Increases in TauSome were correlated with decreases in memory performance and controlled motor speed. The new study, which will begin collections in Phoenix on March 28, will also feature a "Player's Council." The council consists of former NFL athletes who function as advocates for the study, while also providing input to researchers on how to maximize participation from other players.
These studies join similar advances in detecting Fibromyalgia and Parkinson’s, although the latter is currently limited to an invasive spinal tap. Together, they suggest a future in which neurodegenerative diseases can be diagnosed with blood tests. Alzheimer’s, traumatic brain injury, and CTE are progressive conditions in which prompt detection is vital. The ability to diagnose these diseases without prohibitive imaging costs would help clinicians improve the quality of care for patients with a broad range of incomes. Importantly, they could be administered early enough for clinicians to test out therapies, intervene in disease courses, and hopefully improve patients’ quality of life.
Jess is a PhD Candidate in the Neuroscience department at Brown University, and a passionate advocate of science communication and outreach. Her most recent article is a spotlight on Progress in Neural Prosthetics.
 Nakamura, A. et al (2018). High performance plasma amyloid-β biomarkers for Alzheimer’s disease. Nature, 554, pp.249–254.
 Exosome Sciences, Inc. (2018). Study of Blood Test to Detect and Monitor Chronic Traumatic Encephalopathy (CTE) in Former NFL Players Set for Kick-Off in Phoenix.