‟This is a major breakthrough. I believe this blood test can be used clinically in only a few years”, says Oskar Hansson, professor of neurology at Lund University in Sweden, who led the international study.
The study, published in Nature Medicine, involved 580 people and was a collaboration with researchers from Banner Alzheimers Institute and Eli Lilly in the US.
There are two proteins that are known to be linked to Alzheimer's disease – beta-amyloid, which forms what is known as plaque in the brain, and tau, which forms tangles within the brain cells. The new blood test can accurately detect tau pathology in the brain of individuals with early Alzheimer’s, as the blood test detects a special variant of tau which is phosphorylated (P-tau181).
“It is when abnormal tau begins to spread in the brain that the neurons start dying and the affected individuals notice the first symptoms, usually mild memory impairment. However, there are many reasons for memory difficulties besides Alzheimer’s, such as sleep deprivation and depression. With the new blood test, we can now determine which individuals with mild memory complaints have early Alzheimer’s", explains Oskar Hansson.
The study shows that the blood test has both great sensitivity and specificity: it detects about 90 percent of all cases of Alzheimer's and only gave a few false positive results in patients with other dementias.
In addition, the study showed that among non-demented individuals, those with elevated plasma P-tau181 levels had a ten-fold increased risk of developing Alzheimer’s dementia in the years that followed.
“The test can therefore also be used to predict who will develop Alzheimer’s dementia in the coming 4-6 years”, says Shorena Janelidze, first author of the paper.
The new test has a clearly higher diagnostic accuracy compared to other established blood tests, such as the one based on the marker protein NFL (neurofilament light). The test could therefore be of great use when diagnosing patients with memory problems, as soon as the method is approved for clinical use. Considering that blood tests are non-invasive and relatively cheap, the method could be easily implemented in primary care as well as specialized memory clinics worldwide.
“Improved diagnostics for Alzheimer’s could result in better treatment and care of affected individuals, and the test could also facilitate clinical trials evaluating novel therapies for the disease", says Oskar Hansson.
A study led by professor Adam Boxer at University of California San Francisco in the USA found very similar results, which further confirms that the P-tau181 test has a great potential for implementation in clinical practice. The paper by Adam Boxer and collaborators is published in the same issue of Nature Medicine.
Publication in Nature Medicine: Plasma P-tau181 in Alzheimer’s disease: relationship to other biomarkers, differential diagnosis, neuropathology and longitudinal progression to Alzheimer’s dementia