As baby boomers – those born 1948-61 – and other post-world war generations reach old age, the prevalence of Alzheimer’s disease continues to rise. New studies show that the world may be on the cusp of a new, groundbreaking blood test that identifies early-onset and allows treatment to begin before symptoms develop.
Around the world, Alzheimer’s disease is the most common cause of dementia among our ageing populations.
However, accurate diagnosis, particularly during early stages of the disease, is often extraordinarily difficult because the disease shares so many of its symptoms with other conditions.
That may be about to change. Scientific researchers at Sweden’s Lund University have discovered a blood marker that allows doctors to accurately identify the disease in its earliest stages, long before symptoms even arise.
Most importantly, the breakthrough discovery will be, researchers say, generally available sometime during the next few years, as scientists develop an easily usable, approved clinical version.
‟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, who led the international study.
The study, published in the peer-reviewed scientific journal Nature Medicine, involved 580 participants in a cooperative partnership between Lund University and scientists from the Banner Alzheimer’s Institute in the United States and Eli Lilly and Company, a global leader in clinical research and development.
Scientists already know that two proteins are intimately linked to Alzheimer’s disease, a degenerative brain condition that affects memory and cognition. The first is beta-amyloid, a protein that is associated with the formation of abnormal clumps known as amyloid-beta plaques.
The second is a protein known as tau, which causes nerve fibres in the brain to become tangled. Combined, these events eventually cause the death of nerve cells, leading to a progressive decline in memory and thinking skills.
The new blood test developed by Lund University can accurately detect the presence of tau in the brains of patients with early forms of Alzheimer’s by targeting a special variation of tau known as 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”, Oskar Hansson explains.
The study shows that the blood test has both great sensitivity and specificity: it detects about 90 per cent of all cases of Alzheimer’s and only gave a few false-positive results in patients with other dementias. Levels of ptau217 correlated with those who later developed the disease, up to 20 years before symptoms were identified.
Also, the study showed that those with elevated plasma P-tau181 levels had a ten-fold increased risk of developing Alzheimer’s dementia during the following years.
“Therefore, the test can be used to predict who will develop Alzheimer’s dementia in the coming four to six years”, says Shorena Janelidze, first author of the paper.
The new test is more accurate than other available blood tests and maybe most useful 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 the 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.