This article explores the research on blood and imaging biomarkers for early diagnosis of Alzheimer's disease.
Article by Aditi Bagul
Member- Sophomore
Across the globe, approximately fifty million people have Alzheimer's disease or related dementia, yet only 25% of these have been medically diagnosed. Alzheimer's disease, a type of dementia, is a progressive neurodegenerative disorder prevalent in the elderly population. In patients with Alzheimer's disease, cognitive skills and memory decline over time, and the disease is also associated with loss of independence. Alzheimer's disease causes most patients to require caregivers as their condition eventually leads to a disability. In a larger scope, the annual cost of treatment of Alzheimer's disease was $277 billion in the U.S. in 2018 alone. These costs are only associated with healthcare, nursing homes, or family caregivers, and do not take into account lost productivity, disability, or poor quality of life. Currently, there is no definitive cure for this disease, however, the progression can be delayed with medications and risk factor modification. If the disease is identified early enough, there is certainly a role in prolonging the quality of life and function as well as planning for their future. There is ongoing research on potential biomarkers and if they can detect Alzheimer's disease early enough. A biomarker, or a biological marker, is a signal in the body that is associated with a disease process and can be identified even before symptoms manifest. While biomarkers may not be an answer to the cure, they are important quantitative signals that can detect diseases or abnormal conditions within a patient. This effective detection can alert patients before they experience memory loss or find it hard to fulfill daily tasks.
Currently, there are no widely accepted biomarkers for early detection in the general population. However, certain biomarkers are promising such as tau and amyloid proteins and genetic markers. Doctors at present rely on patient symptoms and neuropsychological testing in order to diagnose Alzheimer's disease. Brain imaging through CT or MRI scans helps corroborate the diagnosis based on the shape of the brain surface, reduced size, and position of lesions in the brain. There is certainly promise that using molecular imaging through Positron emission technology (PET) or functional MRI scans (fMRI) can detect proteins associated with Alzheimer's disease and provide clues to early changes in the brain before symptoms appear. There are various imaging compounds that are used in these brain scans to trace amyloid and tau proteins associated with Alzheimer's disease lesions in the brain. Presently, the FDA has approved Neuraceq®, Amyvid®, and Vizamyl®, which are imaging compounds that trace beta-amyloid. Flortaucipir F18 from the brand, Tauvid®, has been approved to detect levels of the tau protein in the brain. Also, tau and amyloid proteins can be traced through blood tests and cerebrospinal fluid. These tests are not currently approved and will need ongoing research to be potential biomarkers.
A common genetic marker in Alzheimer's disease patients is the presence of the apolipoprotein E4 variant. In 2017, the FDA approved genetic at-home tests for families with histories of Alzheimer's disease. Similar to a finger-prick test for diabetes patients, this test can detect the APOE4 genetic variant in an individual's blood. Furthermore, there are several other variant presenilin (PSEN) genes and Amyloid precursor protein (APP) that are found on chromosome 14, 1, and 21: PSEN1, PSEN2, and APP, respectively. These three variants play a major role in the development of Alzheimer's disease and if a child inherits it, they could even develop it prior to the age of sixty-five. These abnormal chromosomes inevitably cause mutations in proteins that can be harmful to the brain. These particular genetic variations can be detected early enough in a high-risk population. Therefore, these individuals can plan ahead of time and work on lifestyle modifications if they detect these genetic variants.
Not only do Biomarkers help diagnose patients during the primary stages or even before symptoms occur, but they have also helped medical professionals understand the progression of Alzheimer's and try out different treatments at various stages. Additionally, if Alzheimer's is detected early, there is a certain role for various risk factor modifications. Substantial costs of Alzheimer's disease are associated with caregiving and nursing home care. Diagnosing the disease earlier can help these individuals plan for their future and preferences, and make a significant difference in the health care costs. Thus, biomarkers can play a pivotal role in early Alzheimer's disease detection through blood tests and imaging. Despite their promise, more research is needed for biomarkers that can identify this risk in the general population.
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