The New Alzheimer’s Blood Test That Could Change Your Life

The test, which is not yet available to the public, has potential to detect Alzheimer’s decades before symptoms appear.

by Sarah Ellis Health Writer

It’s highly likely that if you’re reading this, you know someone affected by Alzheimer’s dementia. In fact, one in 10 people over 65 years old lives with the condition. It is also the sixth leading cause of death in the United States, as well as a leading cause of poor health among those in their elderly years—especially people of color, who are more likely than white people to develop Alzheimer’s or other dementias.

Early diagnosis is a crucial tool to help slow progression of memory loss in older adults. However, Alzheimer’s is challenging to diagnose, due in part to the lack of obvious medical markers to distinguish it from other forms of dementia. “Currently, Alzheimer’s dementia is diagnosed in the doctor’s office, typically using cognitive testing,” explains Rebecca Edelmayer, Ph.D., director of Scientific Engagement for the Alzheimer's Association in Chicago. The disease can only be diagnosed with certainty after death upon examination of brain tissue.

That’s why a new Alzheimer’s diagnostic blood test is making waves in the medical community. A study published in JAMA looked at a blood biomarker called plasma phospho-tau217 with the ability to pinpoint Alzheimer’s decades before symptoms appear. Experts say this could represent a breakthrough in the fight against Alzheimer’s worldwide. “We need those tools and technologies to help diagnose individuals at the earliest stages of their disease,” Edelmayer says, paving the way for better prevention moving forward.

That’s not all – as of early December, a different Alzheimer’s blood test is available by prescription to residents of 45 U.S. states. It hasn’t yet received FDA approval and is thus still in early stages, but it reveals just how quickly this technology is coming our way.

What Makes Alzheimer's Blood Tests So Useful?

Here’s the thing about Alzheimer’s detection: it is typically a diagnosis of exclusion, meaning your doctor will rule out other conditions before deciding you likely have Alzheimer’s dementia.

Edelmayer explains that usually someone will come in with concerns about themselves or a family member, based on symptoms of memory loss they’ve been noticing. The doctor will conduct a series of blood and urine tests, a cognitive questionnaire involving friends and family, and brain scans to rule out things like stroke, brain tumor, Parkinson’s disease, or sleep issues.

Alzheimer’s isn’t the only form of dementia someone can develop. There’s also vascular dementia, frontotemporal dementia, and dementia caused by specific medical conditions like Huntington’s disease, a head injury, mental health issues, HIV complications, and more. The treatment protocol will depend on what type of dementia the person has. For Alzheimer’s, there is no known cure, but there are medications that help preserve memory as well as lifestyle changes that can make a person more alert and comfortable as the disease progresses.

The blood test currently for sale is from a company called C2N Diagnostics, and it is designed for people over 60 years old already experiencing symptoms of cognitive decline. It costs $1,250 and is not currently covered by insurance. The test works by measuring the concentrations of a protein called amyloid beta in the brain, which can signal the onset of Alzheimer’s. It provides each patient with a probability score to assess the likelihood this protein is accumulating – and thus, the likelihood they have Alzheimer’s dementia.

“We’ve been following some of the blood biomarker work for a number of years now,” Edelmayer says, “and it’s really been making remarkable progress.” She explains that this type of technology could have major implications for the ability of clinicians and patients to detect cognitive decline early, and maybe ultimately even work to reverse it.

For now, though, the C2N blood teest is still very new. It has not yet received FDA approval and is being sold through other federal guidelines regarding laboratory manufacturing and safety. “Without the FDA’s ability to review all the data that supports this test for use in a clinic, it’s really unclear how accurate and reliable the test results are,” Edelmayer says. The company’s internal results, based on data from 686 patients, found the test to be 86% accurate at predicting plaque buildup in the brain. But we still need third-party verification and data on a broader scale. “If this test is going out broadly to the public, it’s not perfectly clear whether the results are going to be as predictive across all races, ethnicities, age groups, and people living with different comorbidities,” she notes. “We just don’t know what this test predicts in all these different individuals.” For now, she advises patients approach this test with caution, speaking to their doctor about the potential pros and cons.

More Technology On the Horizon

Other blood tests use a similar method to detect different proteins indicative of dementia. The test reported in JAMA this year focuses on one called tau. “Tau is associated with death of neurons and development of memory impairment in Alzheimer’s disease,” explains Oskar Hansson, M.D., a neurology professor at Lund University in Sweden and a principal author on the blood test study. Dr. Hansson explains that by identifying a specific variant of tau in the blood, researchers can see the extent to which tau is affecting the brain. “The test is specific for Alzheimer’s and is not elevated in other dementia disorders,” he says.

The JAMA study recruited 1,402 participants, some as young as 25, to test them for Alzheimer’s blood biomarkers. Researchers found that this blood test could detect high levels of plasma P-tau217 up to 20 years before cognitive impairment symptoms may begin to appear. “The test is more specific than MRI and cognitive tests, which are often changed in similar ways in other dementia disorders,” Dr. Hansson says.

New research has paved the way for other Alzheimer’s-specific diagnosis tests, like a spinal fluid test presented in a 2018 study in American Family Physician, which can identify the levels of tau affecting the brain. But, as Dr. Hansson explains, these methods are costly and difficult to access, as opposed to the simplicity and ease with which a blood test could be distributed to clinics around the world.

“This is some of the first research to show that these tests may be even more accurate than we ever imagined they could be,” Edelmayer says. She agrees that there is great potential for this test to be widespread and accessible, similar to routine blood tests that can measure cholesterol, STIs, or thyroid function. “There’s more research that’s needed, but it’s still a very exciting time,” she says.

Why Early Detection Matters

This all begs the question: Do I want to know if I’m destined to develop Alzheimer’s disease? With no set cure for Alzheimer’s dementia, there’s an arguable case for not wanting to know that you’ll soon start losing your memory. However, research increasingly shows that early detection of Alzheimer’s risk could be key to slowing or stopping the disease progression altogether.

Multiple clinical trials are in progress looking at whether antibodies can be used to reduce or prevent cognitive impairment. Lifestyle changes such as regular exercise, a whole foods diet, a rich social life, and minimizing vascular disease risk can all help slow Alzheimer’s progression. “There are a lot of benefits to early detection and accurate diagnosis,” Edelmayer says. She explains that early detection gives families the power to plan for the future, as well as an incentive to help their loved one change their lifestyle for the better. “There’s also potential to get enrolled and involved in clinical trials where you might see the most benefit at an earliest phase of the disease,” she notes.

For the C2N test, there is no official guidance as to how to proceed after getting your results. “It’s brand new, and the FDA has not established what the results of the test may mean for you and your care,” Edelmayer says. She suggests approaching your physician before considering anything like this (and since it’s only available by prescription, you’ll have to do this anyway). “When anyone is considering any type of Alzheimer’s or dementia-related testing, it’s really important that they have a conversation with their physician to see if they’re a candidate for that type of test,” she says. “The first conversation that needs to be had is [whether you are] concerned about any issues with memory or thinking.” Once you and your physician have established your specific concerns, you can decide together what your next steps should be.

As for the blood test that measures tau, Dr. Hansson hopes it will open new avenues to learn about slowing Alzheimer’s progression. “I think this test will facilitate the development of disease modifying therapies that hopefully can slow down or even stop the disease,” he says. Participants could participate in trials that track and monitor their symptoms in the long term, giving experts a better idea of how to stop memory loss from occurring.

“It really is an exciting time for the field right now,” Edelmayer says. “These blood tests are just one example of the efforts that are ongoing to support not only detection and diagnosis, but also will help to support the development of new drugs and therapeutics and interventions in the future.” These small steps all play a role in working toward the seminal goal of an Alzheimer’s cure.

Sarah Ellis
Meet Our Writer
Sarah Ellis

Sarah Ellis is a wellness and culture writer who covers everything from contraceptive access to chronic health conditions to fitness trends. She is originally from Nashville, Tennessee and currently resides in NYC. She has written for Elite Daily, Greatist, mindbodygreen and others. When she’s not writing, Sarah loves distance running, vegan food, and getting the most out of her library card.