In the US, currently, about 6 million individuals live with a diagnosis of Alzheimer’s disease, the most common form of dementia in the elderly. Because there is no effective cure, the disease remains one of the most critical public health issues in America and all developed countries.
Prevention and early diagnosis have been considered by doctors and researchers as primary goals in the quest to halt and delay the onset and/or progression of Alzheimer's disease. While preventing a disease is always the best cure, everybody recognizes the intrinsic importance of early diagnosis, not just for Alzheimer's but for any other disease.
Today, an early diagnosis of Alzheimer's disease typically results from a combination of brain imaging techniques, memory assessment tests, and/or the measurement of specific compounds (also known as “biomarkers”) in an individual's cerebral spinal fluid. This same approach is also implemented when evaluating the risk of developing Alzheimer’s disease later in life. In both scenarios, an individual experiencing consistent memory problems, or with a strong family history of the disease would seek a doctor’s attention. The doctor, after the clinical evaluation, would then prescribe the various tests described above, interpret the results, and discuss them with the patient.
A Blood Test
All this could change dramatically since, starting this summer, anyone in the USA could potentially learn about their risk of developing Alzheimer’s disease from a simple blood test, independently of a doctor’s visit.
On July 31, 2023, Quest Diagnostics announced the availability of the AD-Detect Test for Alzheimer’s disease, a blood test that anybody above 18 years old can purchase in most of the USA states.
The test measures the blood levels of the amyloid beta (Abeta) proteins 40 and 42, known to accumulate in the brain of individuals with Alzheimer’s disease, forming what are called “amyloid plaques”. Some evidence suggests that a lower ratio of these two proteins signals more plaques, whereas a higher ratio indicates fewer.
The New Approach
After purchasing the test individual can directly go to a Quest clinic for a blood draw, and later receive the results. But is this result alone sufficient to accurately assess the risk of developing Alzheimer’s disease? The simple answer is “no”. If the test suggests a higher risk, the individual will then need to see a physician, who will most likely prescribe cognitive and brain imaging tests to confirm or refute it.
There is no doubt that knowing one is at higher risk for the disease could encourage them to adopt lifestyle changes known to be beneficial against memory decline and dementia. However, it can also be a significant source of anxiety and psychological stress. Studies have shown that patients can be seriously affected in their feelings and behavior by any test result, particularly in this case, if the result is uncertain.
The Unresolved Issues
Scientists agree that high blood levels of Abeta proteins do not predict nor indicate the risk of developing or currently having the disease. Importantly, the new test, as well as most others that measure these proteins in the blood, has not been evaluated or approved by the Food and Drug Administration.
There is no doubt that the availability of a home test that could help in the early diagnosis and/or risk assessment for Alzheimer’s disease is an important milestone in our fight against the disease. However, in my opinion, we should be very cautious, though optimistic about this development, and never forget some key points which I will try to summarize below.
First and foremost, the blood test alone does not provide enough information to reach a diagnosis of memory problems or cognitive decline. Only a trained physician can do that. The blood test at best will provide only one small piece of information among many others needed for a diagnosis of Alzheimer's disease. Abeta protein is not the only “biomarker” that can predict the onset of Alzheimer’s disease; high levels of tau protein have also been linked to it. Finally, let's not underestimate that besides Alzheimer’s disease, there are other conditions like head trauma, brain tumors, and depression, just to mention a few, that can manifest with memory problems and even changes in the levels of Abeta proteins.
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Domenico Praticò, MD, is the Scott Richards North Star Charitable Foundation Chair for Alzheimer’s Research, Professor and Director of the Alzheimer’s Center at Temple, and Professor of Pharmacology at the Lewis Katz School of Medicine at Temple University You can find out more information on Dr. Domenico Pratico's research papers here. Connect with Dr. Domenico Pratico on LinkedIn, Facebook, Twitter & Instagram.