Written & Researched By: Kamya Patel
As the most well-known form of dementia, Alzheimer’s disease poses a threat to millions of people regularly. Unfortunately, diagnosing the disease is easier said than done. For a while, a confirmed diagnosis could only occur during an autopsy. Nowadays, brain imaging and spinal fluid tests allow doctors to notice symptoms during the initial stage. However, these invasive mechanisms are not only costly but also limited to locations used for research rather than everyday clinics and hospitals. In the last few years, technological advances have led to a better, more efficient way to identify signs of Alzheimer’s disease.
In the fall of 2020, C2N Diagnostics based in St. Louis, Missouri released a blood test called PrecivityAD. Regulated under the Clinical Laboratory Improvement Amendments (CLIA) program managed by the Centers for Medicare & Medicaid Services (CMS), it is one of the first in a new era of early detection methods for Alzheimer’s disease. Specifically, PrecivityAD utilizes mass spectrometry to find particular types of beta-amyloid protein fragments that indicate the presence of Alzheimer’s. These proteins gather to form plaques visible enough on brain scans about two decades before the onset of memory problems. The buildup in the brain causes beta-amyloid levels to decrease in the surrounding fluid, all of which can now be measured through blood.
As of now, PrecivityAD is targeted towards patients 60 to 91 years old with symptoms of cognitive impairment. It is also meant to be used as a supplementary tool for making accurate diagnoses by differentiating between Alzheimer’s and other types of memory loss. In terms of cost, the lack of insurance coverage places the blood test at a price of $1250; however, procedures like a $5000 PET beta-amyloid test or an $800-1000 sample cerebrospinal fluid are a lot more invasive and burdensome for patients.
In addition to observing beta-amyloid, specific types of tau protein can also be an indicator of Alzheimer’s. Due to their role in causing the disease, tau proteins, unlike beta-amyloid, would be more useful in later stages when patients are obviously symptomatic. In a study led by Oskar Hansson at Lund University, Sweden, researchers found that p-tau217 has a diagnostic accuracy between 89 to 98 percent for Alzheimer’s disease. Plus, p-tau217 proved better than blood tests with other experimental biomarkers, such as p-tau181, amyloid beta 42/40, and neurofilament light. In fact, p-tau217 levels were seven-fold higher in Alzheimer’s patients; the presence of a gene causing Alzheimer’s also led to an increase in amounts of p-tau217. Similarly, researchers in a study at the UCSF Memory and Aging Center comparing p-tau181 and p-tau217 concluded that both of these proteins are found in greater amounts in Alzheimer’s and the measurements are as precise as PET scans. Furthermore, scientists at Washington University School of Medicine have launched SEABIRD (Study to Evaluate Amyloid in Blood and Imaging Related to Dementia) to verify blood-based biomarkers for Alzheimer’s in clinical trials with diverse participants varying in race, socioeconomic status, medical history, and cognitive ability.
The development of these new blood tests also comes with more positive implications. Not only can physicians determine which patients are at risk but researchers could also use the tests to confirm Alzheimer’s for experimental drug participants. Using the beta-amyloid or tau protein blood tests would help save time and money when it comes to procedures in clinical trials testing potential cures and treatments. Moreover, early detection makes it possible to test preventative drugs as well. These revolutionizing blood tests are the first of their kind and especially the first in a generation of techniques to combat the most common neurodegenerative disease.
Resources
“A Blood Test for Alzheimer's? Markers For Tau Take Us a Step Closer.” Alzheimer's Association International Conference, 28 July 2020, https://www.alz.org/aaic/releases_2020/blood-biomarkers-tau.asp.
Landhuis, Esther. “Detecting Alzheimer's Gets Easier with a Simple Blood Test.” Scientific American, Scientific American, 4 Feb. 2021, https://www.scientificamerican.com/article/detecting-alzheimers-gets-easier-with-a-simple-blood-test/.