A new study suggests that a simple blood test could be used to screen for Alzheimer’s disease with high accuracy, even before symptoms begin to show. The test measures a type of protein called phosphorylated tau, or p-tau, which increases in the blood as the disease progresses.
P-tau is a key biomarker of Alzheimer’s disease, which is the most common type of dementia. Alzheimer’s disease affects memory and thinking skills, and is caused by the buildup of two damaging proteins in the brain: beta amyloid and tau. Beta amyloid forms sticky plaques that interfere with communication between brain cells, while tau forms tangled fibers that disrupt the transport of nutrients and signals within the cells.
The current methods to detect the buildup of beta amyloid and tau in the brain are either invasive, such as a spinal tap, or expensive, such as a brain scan. These tests are often inaccessible and costly for many patients, especially in the early stages of the disease when treatment could be more effective.
A blood test that can measure p-tau levels could offer a cheaper, faster, and more convenient way to screen for Alzheimer’s disease, and potentially identify people who are at risk of developing the disease before they show any signs of cognitive decline.
How accurate is the blood test?
The study, published in the journal JAMA Neurology, involved testing blood samples from 1,402 participants from Sweden, Colombia, and the United States, who were either healthy, had mild cognitive impairment, or had Alzheimer’s disease. The researchers used a commercially available tool called the ALZpath pTau217 assay, which was developed by the company ALZpath, to measure the levels of p-tau in the blood.
The results showed that the blood test was up to 96% accurate in identifying elevated levels of beta amyloid in the brain, and up to 97% accurate in identifying tau tangles, which are more specific to Alzheimer’s disease. The blood test was also able to distinguish Alzheimer’s disease from other types of dementia, such as frontotemporal dementia and vascular dementia, with high accuracy.
The blood test was also able to detect p-tau levels in people who had a genetic mutation that causes early-onset Alzheimer’s disease, up to 16 years before they developed symptoms. This suggests that the blood test could be used to monitor the progression of the disease and the effectiveness of treatments in clinical trials.
What are the implications and limitations of the study?
The study is one of the largest and most comprehensive to date to evaluate the performance of a blood test for Alzheimer’s disease. The researchers said that the blood test could be a game-changer for the field of Alzheimer’s research and care, as it could enable earlier diagnosis, intervention, and prevention of the disease.
However, the study also has some limitations that need to be addressed before the blood test can be widely used in clinical practice. For example, the study did not include people from diverse ethnic and racial backgrounds, who may have different risk factors and genetic variations for Alzheimer’s disease. The study also did not compare the blood test with other blood-based biomarkers, such as p-tau181 and neurofilament light chain, which have also shown promise in detecting Alzheimer’s disease.
The researchers said that more studies are needed to validate the blood test in different populations and settings, and to determine the optimal cut-off values and frequency of testing for p-tau levels. They also said that the blood test should not be used as a standalone diagnostic tool, but rather as a screening tool that can complement other clinical assessments and tests.