A simple blood test could open the possibility of determining the presence and progression of Alzheimer's disease without complicated and uncomfortable brain imaging or cerebrospinal fluid tests. This marks the first recommendation from experts that blood tests could be used for Alzheimer's disease diagnosis instead of existing high-cost, high-risk tests. It is expected to significantly lower the diagnosis threshold for the elderly.
The Alzheimer's Association, the world's largest Alzheimer's disease conference, announced preliminary clinical guidelines for using blood tests in diagnosis at the 'Alzheimer's Association International Conference (AAIC)' held in Toronto, Canada, on the 29th (local time).
The crux is that blood tests, which have a positive predictive accuracy for identifying actual patients and sensitivity and specificity both exceeding 90%, could replace existing diagnostic methods like positron emission tomography (PET) or cerebrospinal fluid tests. This guideline was also published in the international journal 'Alzheimer's & Dementia,' published by the Association.
Alzheimer's disease is a representative degenerative brain disorder characterized by the gradual deterioration of cognitive functions such as memory and reasoning as brain neurons are progressively damaged. It is common, accounting for about 60-70% of dementia cases worldwide; however, there are still no fundamental treatments available, making early diagnosis and continuous management essential.
According to the Alzheimer's Association's guidelines, blood tests with a sensitivity of over 90% and specificity of over 75% can also be used as a primary screening test. In this case, if the result is positive, the likelihood of Alzheimer's disease is high, but if negative, the accuracy is low, so confirmation through existing precision tests is necessary.
These guidelines do not apply to early screening tests for the general public. They are applicable only to patients with cognitive impairment who are receiving medical consultations. The Association emphasized that blood tests cannot replace a physician's clinical evaluation and should be used as an auxiliary tool in the diagnostic process.
Currently, there is only one blood test approved by the U.S. Food and Drug Administration (FDA), but demand for blood-based diagnostics is increasing as the pace of new drug development accelerates. Pharmaceutical companies such as Japan's Eisai and America's Biogen, which developed the Alzheimer's treatment 'Leqembi,' as well as Eli Lilly, the development company of 'Keyzyl,' are also introducing methods to link diagnostics and prescriptions using remote medical platforms. Both treatments have shown efficacy in early patients, and if early diagnosis can be achieved, the number of patients who can use them may increase.
However, experts believe it is still too early to make treatment decisions based solely on blood tests. They point out that blood tests have difficulty in precisely analyzing amyloid-beta proteins, which are identified as one of the main causes of Alzheimer's disease. Amyloid beta is originally protective of neurons, but when it escapes outside brain cells and clumps together, it can destroy neurons instead.
Stephen Salloway, a professor of neurology at Brown University in the U.S., said, "Current drug treatments aim to reduce amyloid beta plaques, which are identified as one of the main causes of Alzheimer's disease," adding that "it is necessary to confirm the reduction of amyloid beta through PET scans before and during treatment." He also noted that "blood tests can determine the presence of amyloid beta, but precisely measuring the quantity accumulated in the brain or therapeutic effects is difficult."
To create these guidelines, the Association reviewed about 50 studies. They excluded studies that included individuals without cognitive impairment and analyzed only those tests that accurately determined positivity and negativity with clear standard values. The reliability of the scientific basis for each test was also evaluated. Information on the accuracy of each test will be organized in an online portal and continuously updated.
References
Alzheimer's & Dementia(2025), DOI: https://doi.org/10.1002/alz.70535