A commercially available blood test has now been trialled in routine healthcare. "The blood test showed about 90% reliability even in primary care. This may have major implications for all those individuals who seek help for memory loss and suspected Alzheimer's," say the researchers at Lund University in Sweden behind the study.
Alzheimer's disease affects one in five women and one in ten men over their lifetimes, but diagnostic tools remain cumbersome and often inaccessible in primary care. While specialist memory clinics often utilize advanced diagnostic methods such as PET scans and cerebrospinal fluid tests, there is a pressing need for simpler and quicker diagnostic tools for use in primary care.
The research into this innovative blood testing method, which measures levels of Plasma Phospho-Tau217, began in 2019. The studies indicate that the blood test can detect Alzheimer's-related changes before symptoms are evident and track progression as the disease advances.
Earlier this year, findings demonstrated that this blood test is as reliable as, and in some cases superior to, cerebrospinal fluid tests in diagnosing the disease. The current study, published in the prestigious journal JAMA, shows for the first time the test's reliability when used in routine healthcare settings, including both primary and specialist healthcare.
"The blood test can determine with 90% accuracy whether a person experiencing memory loss is suffering from Alzheimer's," stated Sebastian Palmqvist, Associate Professor of Neurology at Lund University and a consultant at Skåne University Hospital, who co-led the study with Professor Oskar Hansson.
The study included 1,213 individuals experiencing mild memory symptoms, a potential early sign of Alzheimer's. Of these, 515 were evaluated in primary care and 698 in a specialist memory clinic. These patients were tested using the blood test, and the test results were then confirmed with cerebrospinal fluid tests that can indicate Alzheimer's disease pathology.
"Early diagnosis is crucial as new treatments that slow the disease's progression are developed," explained Professor Hansson. "For example, two immunotherapies have recently been approved in the USA and are expected to be available in Europe soon. An early and accurate diagnosis is also vital for facilitating research into new treatments."
The blood test's reliability of about 90 per cent in identifying Alzheimer's disease was compared with doctors' assessments within primary or specialist care before they were allowed to see the results of the blood test or cerebrospinal fluid test.
"Primary care doctors' accuracy in identifying Alzheimer's disease was 61 per cent, while specialist physicians were correct 73 per cent of the time. This underscores the lack of good, cost-effective diagnostic tools, particularly in primary care, and indicates the potential improvement in diagnosis with the adoption of this blood test in healthcare settings," added Sebastian Palmqvist.
The simplicity and reliability of this blood test make it a significant advancement in diagnosing Alzheimer's, offering a straightforward method to rule out the disease in primary care. This is crucial as memory loss can also stem from other treatable conditions such as depression or chronic fatigue.
"The next steps include establishing clear clinical guidelines for the blood test's use in healthcare," concluded Hansson. "The test is already available in the USA and is likely to become available in many other countries soon. Initially, it will mainly be used in specialist memory clinics, and it may take approximately one to two years to implement guidelines and training in primary care."
Publication
"Blood Biomarkers to Detect Alzheimer Disease in Primary Care and Secondary Care"
JAMA, 28 juli 2024, DOI: 10.1001/jama.2024.13855
The study has been supported by e.g. the Alzheimer's Association and the National Institute of Ageing, European Research Council, The Swedish Research Council, Knut and Alice Wallenberg Foundation, the Swedish Alzheimer Foundation, EU Joint Programme - Neurodegenerative Disease Research (JPND).
Facts about the blood test
The blood test shows positive or negative results for Alzheimer's disease but can also indicate if the result is unclear and further investigation with a PET-camera or cerebrospinal fluid test is required for a more secure diagnosis.
The blood test measures the relationship between phosphorylated and non-phosphorylated versions of the tau217 protein, a biomarker in the blood that is specific to Alzheimer's disease. Tau is a protein that stabilises a structure in the cells called microtubules, which are important to the transport system within the cell. In Alzheimer's disease, the tau proteins become hyperphosphorylated and then form neurofibrillary tangles, which are strongly linked to cognitive ability being affected. Phosphorylation means that one or more group of phosphates binds to the protein.
The study is underway at more than 20 health centres in south-west Skåne and the memory clinic at Skåne University Hospital.
