Blood Testing & Genetic Testing for Alzheimer’s and / or Dementia

Last Updated: July 24, 2018

Alzheimer’s Blood Tests

Recently there has been significant press coverage about blood tests that can detect Alzheimer’s prior to onset of physical symptoms. The media hype is justified given the impact such a test will have and since there is not just one blood test in development, but at least three different blood tests and even a retinal test. For families that suspect a loved one may have Alzheimer’s, this is very good news. Unfortunately, this news can be misleading and bring false hope. There are multiple tests and the results have been promising, but the reality is that families need a test that is available today. Waiting for the development of a blood test is not an option, however promising that test may be. While this article will discuss Alzheimer’s / dementia blood tests, their benefits and alternatives, readers should be aware that Alzheimer’s blood tests are probably, a minimum of 5 years away from being commercially available in the United States. The most optimistic estimates have them appearing on the market in the early 2020s. To be clear, one may hear of persons receiving Alzheimer’s blood tests, but these persons would almost certainly be in a clinical trial setting.

 Definitive blood tests for Alzheimer’s are several years away at a minimum.


Alzheimer’s Genetic Tests

Genetic testing for Alzheimer’s or other related dementias is misleading in a different way than blood tests. While blood tests will offer (hopefully) a definitive diagnosis, genetic testing will only reveal a propensity for developing Alzheimer’s. To be clear, a genetic test will tell the individual if they have the presence of a gene or of a genetic mutation that has been found to be linked to Alzheimer’s. By no means does having the gene or mutation guarantee that the individual will develop Alzheimer’s.

It is worth noting that there are multiple types of dementia, well beyond Alzheimer’s and the genetic markings for these different types of dementia are different. Furthermore, some types of dementia, such as dementia resulting from Huntington’s disease are much more likely to have a hereditary component. Therefore, genetic testing for dementia is 1) not definitive, and 2) the propensity to develop dementia varies with the type of dementia one might develop.

Genetic testing for dementia differs from blood testing in another significant way. Genetic testing is available today, no prescription is required, and these tests are relatively inexpensive. They can easily be taken at home simply with a saliva swab. As of summer, 2018, one could expect to pay only between $100 – $200.


Alzheimer’s / Dementia Testing Alternatives

Despite the lack of a definitive blood test, families who suspect their loved one may have Alzheimer’s have a well-trod, if meandering, 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 or even some interactive tests that might provide immediate results.  However, these online tests do not actually test for Alzheimer’s or dementia.  Instead what they offer families are answers to the questions “Are my concerns about my loved one justified?” Or “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 (commonly referred to as a Spinal Tab) when coupled with multiple physicians’ consultations can make a diagnosis of Alzheimer’s with upwards of 90% 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.


Future of Alzheimer’s Blood Tests

When they arrive in the US (and by the way despite many rumors to the contrary, blood tests for Alzheimer’s are not available elsewhere in the world either), they will significantly impact the way doctors diagnosis and even treat the condition. There are multiple blood tests in development, some are looking at fat in the blood, several others are looking at blood proteins.  Some of these are targeting the detection of Alzheimer’s 3 years in advance of symptoms and others may actually be able to detect the condition as far as 10 years in advance of physical symptoms.  Regardless of the approach, blood tests will significantly speed up the diagnosis process.  Lab work will be able to detect Alzheimer’s in a 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 and / or a painful spinal tab, will simply give a blood sample.  Because a blood test is a highly automated process, diagnosing Alzheimer’s becomes an inexpensive process instead a time-consuming one that involves multiple specialists.   High accuracy allows for definitive answers instead of families seeking multiple opinions from even more specialists.

Lastly, because blood tests will allow us to receive a diagnosis of Alzheimer’s long before we start to show any symptoms of the condition, it will very likely change how we treat the condition.  Instead of a focus on symptom management (as there is today for Alzheimer’s) the focus switches to how we can prevent or delay the condition from progressing to a point where symptoms begin to impact the life of the patient.


What’s Taking So Long?

Everyone is impatient for a blood test to arrive; patients and families as much as researchers and doctors. So why will it take so long to have a definitive blood test on the market.  Part of the reason is the testing process.  When a blood test is first developed, it is tested against persons currently known to have Alzheimer’s.  However, the goal is not just to accurately test for Alzheimer’s, but to identify persons well in advance of when they show symptoms.  If a test correctly identifies those who already have Alzheimer’s, then it is tested against persons who do not currently have the condition.  If the researchers are hoping to identify the condition 3 years in advance of showing symptoms, then they must wait 3 years to determine if the test is working and if it is not, they must start all over again.   If they hope to identify the disease 10 years before symptoms, then they must wait 10 years.