It’s true that a blood test for Alzheimer’s disease (AD) has been developed. It appears capable of accurately diagnosing the condition as long as 20 years before symptoms appear and may help identify the condition early in people with a genetic mutation that causes the disease. Reportedly, the test also can help differentiate Alzheimer’s from other types of dementia. While it is not yet ready for prime time, experts predict that it could be available within two to three years.
Alzheimer’s is a progressive disease in which healthy brain tissue degenerates, resulting in problems with memory, cognition, and behavior. It is the most common cause of dementia (loss of memory and other intellectual abilities serious enough to interfere with daily life) and the seventh-leading cause of death in the United States.
The new test for the disease measures a form of the tau protein found in tangles that spread through the brain and are regarded as the defining physical features of AD. At present, these changes can be detected only via PET scans (positron emission tomography) or by measuring amyloid and tau proteins in spinal fluid, methods considered expensive, invasive and often not easily accessible and not covered by insurance.
According to information presented at the Alzheimer’s Association conference in August (2020), the new test proved accurate in a study involving 1,402 people from Sweden, Columbia and the U.S. It worked better than MRI brain scans, was as good as PET scans or spinal taps and reportedly was almost as accurate as autopsy evidence. Nearly six million people in the U.S. and some 30 million worldwide have Alzheimer’s, a number that is expected to more than double by 2050.
Today, AD can be diagnosed only via assessments of memory and cognitive impairment as well as information provided by family members and caregivers. Because cognitive impairment can be caused by other conditions, the diagnoses are not always accurate.
Maria Carrillo, the Alzheimer’s Association’s chief science officer, noted that while information on the new test presented at the July conference is encouraging, “We do not yet know how long it will be until these tests are available for clinical use.” At present, Alzheimer’s disease is typically diagnosed after doctors rule out other conditions.)
Andrew Weil, M.D.
Sebastian Palmquist et al, “Discriminative Accuracy of Plasma Phospho-tau217 for Alzheimer Disease vs Other Neurodegenerative Disorders,” JAMA, July 28, 2020, doi:10.1001/jama.2020.12134