As of writing, there are two blood tests for Alzheimer’s available in the US: Preclivity AD Test and Quest AD- Detect. While neither have FDA approval, they are lab certified for reliability and are or will be seeking FDA approval. The main drawback through these non-invasive blood tests is that most insurance companies will not cover the cost of them because they are not FDA approved. So, this becomes an out-of-pocket expense. Below is a table that outlines both tests in terms of how much they cost, what they test for and how to get them done.
|Blood Tests for Alzheimer’s Disease (Updated May 2022)|
|Test||Cost||How it works||Where to get it|
|Preclivity AD Test from C2N Diagnostics||$1250
|Measures proteins in blood plasma. Testing for beta amyloid protein build up to indicate Alzheimer’s diagnosis. Specifically, checking the ratio of 2 different amyloid beta proteins (42/40) that are biological markers of the disease. It also detects a genotype (ApoE) that is also an indicator for the onset of Alzheimer’s. Results take approximately 10 days.||Available through a doctor’s order in all states except New York.|
|Quest AD- Detect from Quest Diagnostics||$500||Measures amyloid beta proteins in blood plasma. Designed similarly to detect the ratio of 2 amyloid beta proteins, beta40 and beta42. The test is meant to determine the risk for Alzheimer’s by looking at if there is a higher or lower level of this protein in the blood.||Available by a doctor’s order but only at Quest Diagnostic labs nationwide.|
Two different blood tests have been granted FDA breakthrough device status recently but are still not available to the general public. That means that they are fast tracked in their approval process by being able to conduct clinical trials faster and share their information with the FDA quicker.
The first is Diadem’s AlzoSure Predict. It was granted FDA breakthrough device status in early 2022. This blood test is different because it is a preventative diagnostic. It can predict if a patient with little to no symptoms (of cognitive impairment) will develop Alzheimer’s disease in the next 6 years. This is done by testing “bio markers”. A protein called p53 is checked along with how it reacts to an antibody and binds to it. High levels of p53 have been shown through lots of studies to be a sign of the disease before the appearance of its symptoms. To date, Phase 1 was completed with 482 participants and showed a 98% success rate in correctly predicting Alzheimer’s disease. This was done by retesting patients’ blood after 36, 72 and 90 months. It is estimated that a clinical trial for Phase 2 will begin later in 2022 testing 1,000 patients. In addition, AlzoSure Predict has also been granted special approval in Europe that enables it to be sold as further studies take place.
The second test is Simoa (or SiMoA, for “single molecule array”). It was also granted FDA breakthrough device status in late 2021 and tests for proteins in blood plasma. It’s the same idea as other blood tests: identify “biomarkers” in the blood that can usually only be seen via expensive or difficult exams including PET brain scans, MRIs, and spinal taps. The specific protein Simoa can detect is called ptau181, and has been linked to the changes caused by dementia in the brain. In studies, the Simoa was found to be as good at predicting the development of dementia as PET scans and a spinal tap, without the cost, pain, or radioactivity associated with those tests. The test can also detect upcoming dementia-caused brain changes in both the short (within 15 months) and longer (four years) terms. Right now, this technology is used by researchers to identify people who are good candidates for clinical trials so it is not available to most patients.
Genetic testing for Alzheimer’s or other related dementia is somewhat misleading. While blood tests will offer a definitive diagnosis, genetic testing only reveals a propensity for developing Alzheimer’s. Genetic tests reveal the presence of a gene or genetic mutation that has been linked to Alzheimer’s. By no means does having the gene or mutation guarantee that the individual will develop Alzheimer’s.
There are multiple types of dementia, well beyond Alzheimer’s, and the genetic markings for these other types of dementia are different. Some types of dementia, such as dementia resulting from Huntington’s disease, are more likely to have a hereditary component. Genetic testing for dementia is therefore not definitive, and the propensity to develop dementia varies with the type of dementia one might develop.
Despite the lack of FDA approved blood tests, families who suspect their loved one may have Alzheimer’s have a long path to a diagnosis. To begin the process, there are online tests for Alzheimer’s that can be downloaded, printed, completed and taken to your doctor, and even some interactive tests that might provide immediate results. However, these online tests do not actually test for Alzheimer’s or dementia. Instead, they offer families answers to these questions: “Are my concerns about my loved one justified?” “Is this just normal aging or is there something more going on?” Officially, the tests are looking for Mild Cognitive Impairment (MCI). These tests are not definitive, but they can help a family figure out what their next step should be.
If a doctor suspects a patient may have Alzheimer’s, there are more definitive approaches. Brain scans and tests on extracted spinal fluid (a costly and painful procedure commonly referred to as a spinal tap) when coupled with multiple physicians’ consultations can make a diagnosis of Alzheimer’s with upwards of 90 percent accuracy. Families should expect their loved one to be evaluated by a neurologist, a psychiatrist, and very likely a psychologist as well. Since Alzheimer’s is so common among the elderly, a diagnosis is less about finding a condition which fits and more about eliminating other possibilities.
When blood tests become mainstream, they will significantly impact the way doctors diagnose and treat the disease. Medicine and technology have progressed so that it is estimated in the near future to be an easily accessible option.
Beyond the Preclivity AD, Quest AD-Detect, AlzoSure and Simoa, there are multiple other types of blood tests in development. Some are looking at protective fats (called fatty amides) in the blood. Research shows that an increase in fatty amide levels indicates more beta amyloid in the brain. Beta amyloid plaques have been found in the brains of people with Alzheimer’s. Healthy brains eliminate beta-amyloids before they turn to plaque.
Other blood tests will measure proteins such as tau proteins and the neurofilament light chain (NfL) protein. Researchers have found that neuron (brain cell) death, characteristic in people with Alzheimer’s, may be detected by the corresponding increase of these proteins in the blood.
It is also possible that the probable link between insulin resistance, diabetes and Alzheimer’s means blood tests could show the disease in someone well before symptoms occur. Another protein called IRS-1 is commonly associated with diabetes but has also been linked to Alzheimer’s. Studies have shown that someone with Alzheimer’s has more IRS-1 than even someone with diabetes.
Some of these are targeting the detection of Alzheimer’s three years in advance of symptoms, while others may detect the condition as far as 10 years in advance of physical symptoms. Regardless of the approach, blood tests significantly speed up the diagnosis process. Lab work will be able to detect Alzheimer’s in as little as 24 hours, compared with the many months it currently takes to receive a diagnosis. Patients, instead of being subject to a PET scan or a painful spinal tab, will simply give a blood sample. Because a blood test is a highly automated process, diagnosing Alzheimer’s becomes inexpensive and easy rather than time-consuming and involving multiple specialists. High accuracy allows for definitive answers, not families seeking opinions from multiple specialists.
Potentially blood tests will allow patients to receive a diagnosis of Alzheimer’s long before they start to show any symptoms. This can lead to a change in treatment. The current strategy for combating Alzheimer’s is symptom management. Potentially the focus could shift to preventing or delaying the disease from progressing, so symptoms do not impact the life of the patient.
Another interesting finding in the study of Alzheimer’s is related to the eye. Researchers have found that people with Alzheimer’s have a part of their retina that is thinner than in people without the disease. It may be possible that a basic eye exam could, in the future, tell whether someone has Alzheimer’s or another dementia. And some of the proteins associated with Alzheimer’s (described above) can also be detected in eye fluid in the front part of the eye.
Advances in artificial intelligence have researchers excited about the potential for AI to predict the likelihood of developing Alzheimer’s, using only a blood sample and the answers to some basic questions about health.
Promising developments have also been made in determining whether someone will develop Alzheimer’s based on their voice and the way they write. Neuropsychologists are analyzing voice recordings from people with dementia, and finding that the subtle differences in speech, including word choices and complexity of sentences. This may be indicative of the disease. Differences in pen strokes, such as pauses someone takes when asked to draw a clock for the clock test, are another possible indicator.
Everyone is impatient for blood tests to become mainstream; patients and families as much as researchers and doctors. So, why does it take so long?
Part of the reason is the testing process. When a blood test is first developed, it is tested against people who have Alzheimer’s. If a test correctly identifies those who already have Alzheimer’s, then it is tested against people who do not currently have the condition but may be genetically predisposed to developing it. The process is also lengthy because if the researchers are claiming to identify the disease three years in advance of showing symptoms, then they must wait three years to determine if the test is working. If it is not, they start all over again. If they hope to identify the disease 10 years before symptoms, then they must wait 10 years.