Given the opportunity, 90% of Americans say they would take a blood biomarker test for Alzheimer’s disease (AD) — even in the absence of symptoms. Notably, 80% say they wouldn’t wait for a physician to order a test, they’d request one themselves.

The findings, from a recent nationwide survey by the Alzheimer’s Association, suggest a growing desire to predict the risk for or show evidence of AD and related dementias with a simple blood test. For consumers with the inclination and the money, that desire can now become reality.

Once limited to research settings or only available via a physician’s order, blood-based diagnostics for specific biomarkers — primarily pTau-217 and beta-amyloid 42/20 — are now offered by at least four companies in the US. Several others sell blood-based “dementia” panels without those biomarkers and screens for apolipoprotein (APOE) genes, including APOE4, a variant that confers a higher risk for AD.

The companies promote testing to all comers, not just those with a family history or concerns about cognitive symptoms. Test prices range from hundreds to thousands of dollars, depending on whether they are included in a company membership, often designed to encourage repeat testing. Blood draws are conducted at home or at certified labs. Buyers don’t need a prescription or to consult with a physician after receiving results.

Knowing results of such tests could be empowering and may encourage people to prepare for their illness, Jessica Mozersky, PhD, assistant professor of medicine at the Bioethics Research Center at Washington University in St. Louis, told Medscape Medical News. A direct-to-consumer (DTC) test also eliminates potential physician-created barriers to testing, she added.

But there are also potential harms.

Based on results, individuals may interpret everyday forgetfulness — like misplacing keys — as a sign that dementia is inevitable. This can lead them to change life plans, rethink the way they spend their time, or begin viewing their future negatively. “It creates unnecessary worry and anxiety,” Mozersky said.

The growing availability of DTC tests — heralded by some experts and discouraged by others — comes as AD and dementia specialists continue to debate whether AD diagnostic and staging criteria should be based only on biomarkers or on criteria that includes both pathology and symptomology.

For many, it raises a fundamental concern: If experts haven’t reached a consensus on blood-based AD biomarker testing, how can consumers be expected to interpret at-home test results?

In 2024, the number of people living with AD passed 7 million. A recent report from the Alzheimer’s Association estimates that number will nearly double by 2060.

The demand for testing also appears to be rising. Similar to the findings in the Alzheimer’s Association’s survey, a small observational study published last year showed that 90% of patients who received a cerebrospinal fluid AD biomarker test ordered by a physician said the decision to get the test was “easy.” For 82%, getting results was positive because it allowed them to plan ahead and to adopt or continue healthy behaviors such as exercise and cognitive activities.

Until now, blood biomarker tests for AD have primarily been available only through a doctor. The tests measure beta-amyloid 42/20 and pTau-217, both of which are strong biomarkers of AD. Some other blood-based biomarkers under investigation include neurofilament light chain (NfL) and glial fibrillary acidic protein (GFAP).

As reported by Medscape Medical News, the FDA approved the first blood-based AD diagnostic test in May. The Lumipulse G pTau 217/Beta-Amyloid 1-42 is for the early detection of amyloid plaques associated with AD in adults aged 55 years or older who show signs and symptoms of the disease. But it is only available by prescription.

Quest Diagnostics tested the DTC market in 2023, promoting a consumer-initiated test for beta-amyloid 42/40 that had previously been available only through physicians. It was not well-received by clinicians and ethicists. The company withdrew it later that year but continues to sell beta-amyloid 42/20 and pTau-217 tests through physicians, as does its competitor Labcorp.

Today, at least a handful of companies in the US market AD biomarkers directly to the public: Apollo Health, BetterBrain, Function Health, Neurogen Biomarking, and True Health Labs. None of the companies have disclosed ties to pharmaceutical or device companies or test developers.

Some companies direct customers to a lab for blood sample collection, whereas others send a technician to customers’ homes. The extent of biomarker testing and posttest consultation also vary by company.

Apollo Health customers can order a “BrainScan” for $799, which includes screens for pTau-217, GFAP, and NfL. Buyers get a detailed report that explains each test, the result (in nanograms per liter) and optimal range (ng/L) and potential next steps. A pTau-217 result in the normal range, for instance, would come with a recommendation for repeat testing every 2 years. If someone receives an abnormal result, they are contacted by a health coach who can make a physician referral.

At Function Health, members pay $499 a year to have access to hundreds of tests and a written summary of results by a clinician. All of its “Brain Health” tests, including “Beta-Amyloid 42/40 Ratio,” pTau-217, APOE, MTHFR, DNA, and NfL, are available for an additional undisclosed charge.

BetterBrain has a $399 membership that covers an initial 75-minute consultation with cognitive tests, a “personalized brain health plan,” and a blood test that is a basic panel without AD biomarkers. A $499 membership includes all of that plus an APOE test. A pTau-217 test is available for an additional undisclosed fee.

At Neurogen Biomarking, which started in January, a consumer orders an at-home test kit, and a phlebotomist comes to their home for a blood draw. The consumer then fills out an online cognitive assessment. Test results are reviewed by a board-certified neurologist and discussed with the consumer via a virtual visit. If the person is at low-risk, they are given some educational material. Those at higher risk are referred to Neurogen’s “team of specialty-trained neurologists” for continuing care. Testing costs were not provided by the company.

Consumers can order “Beta-Amyloid 42/40” for $749 and pTau-217 for $229 directly through True Health Labs. No consultations or services are offered.

It’s unclear where DTC tests fall in terms of regulation. The FDA does not usually review at-home tests for low-risk medical purposes but will generally do so for diagnostics that are for higher-risk conditions “to determine the validity of test claims,” according to the agency’s website.

Consumers, however, don’t usually have easy access to information on biomarker tests’ sensitivity, specificity, or other characteristics that would be used by clinicians or regulatory authorities to assess a test’s validity.

The lack of regulation of consumer-initiated AD testing is one issue cited by critics of at-home tests, including the Alzheimer’s Association.

“None of these tests have been scientifically proven to be accurate,” the association noted in a statement, adding that “the tests can have false positive results, meaning that individuals can have results saying they have dementia when in fact they do not.”

“For these and other reasons, the Alzheimer’s Association believes that home screening tests cannot and should not be used as a substitute for a thorough examination by a skilled physician. The whole process of assessment and diagnosis should be carried out within the context of an ongoing relationship with a responsible and qualified healthcare professional,” the statement said.

The association also said that biomarker tests should not be ordered — even by physicians — for asymptomatic individuals.

The American Academy of Neurology (AAN) does not have a position on DTC tests for AD biomarkers, a spokesperson told Medscape Medical News. In a 2021 paper on ethical considerations for diagnosis and care, an AAN committee said that biomarker testing could be clinically useful for some symptomatic patients, but testing asymptomatic individuals is “recommended solely in a research setting” because of potential harms “and the absence of interventions capable of favorably altering the natural history of the disease.”

Eric Topol, MD, chair of the Department of Translational Medicine at Scripps Research in La Jolla, California, is bullish on the potential for blood-based biomarker tests. In a blog post, he called the pTau-217 biomarker “one of the most exciting advances in neurology for decades, giving us a new opportunity to accurately predict and potentially prevent (or at least substantially delay) mild cognitive impairment and Alzheimer’s.”

But, wrote Topol, who is the former editor in chief of MedscapeMedical News, “I don’t think these biomarkers are going to be useful in people at low risk.” He wrote that testing should not be used by people who are “cognitively intact” or to tell someone they have pre-AD. “More work needs to be done to determine whether lowering one’s pTau-217 will alter the brain plaque progression and be seen as a disease-modifier,” wrote Topol.

Some people don’t want to know their biomarker status. In a study in May in JAMA Network Open, Mozersky and colleagues reported that while 81% of a group of cognitively normal participants in a longitudinal study of dementia said they wanted to see results, only 60% ultimately opted to get results after testing. Participants said they did not want to know because they didn’t want to become a burden on their family or that they felt fine; others had concerns about whether the tests were accurate.

That low number “surprised us,” said Mozersky. “Our study certainly suggests that when you’re really faced with knowing, that your answer is more likely to possibly be no,” she added.

DTC companies tell buyers that results could motivate them to change their lifestyle to reduce their future risk for AD and dementia. But some participants in Mozersky’s study said they didn’t want to know their status because there were no preventive treatments. Test results weren’t seen as “actionable,” she said.

Some studies have shown a degree of fatalism in individuals after receiving a test result, whether it’s positive or negative.

A group of Israeli researchers studied responses of people given PET scans to detect beta-amyloid. Before testing, all participants said they were motivated to adopt lifestyle changes to fight dementia. However, after testing, both those who had elevated beta-amyloid and those who did not reported a much lower desire to change their lifestyle. Those with normal scans probably felt relieved, wrote the researchers. The group with abnormal scans was too small to fully understand their reaction, they wrote.

Concerns about insurance coverage might also deter potential test-takers. Overall, 44% of those responding to the Alzheimer’s Association survey said they were worried that insurers might not cover healthcare costs in the future if they had received a positive test earlier. Respondents also worried about test accuracy, the cost of testing, and whether a positive test might lead to a prohibition on some activities, like driving.

The DTC companies promise buyers that results will be private and won’t be shared with insurers — or with clinicians. And that raises another issue for many who are concerned about the lack of a physician intermediary with at-home testing.

“You remove the opportunity for clinicians to both review the result and figure out how to interpret it before it’s communicated to the patient,” Jalayne J. Arias, JD, a bioethicist and associate professor of Health Policy and Behavioral Sciences at Georgia State University, Atlanta, told Medscape Medical News.

Many in the field have been “thinking really carefully about how do we provide guidance to clinicians about biomarker testing,” she said. “Those issues are just heightened when we put it into a direct-to-consumer model,” Arias said.

Arias — who with colleagues published an analysis of potential insurance issues with biomarker tests in JAMA Neurology — said that prohibitions against discrimination based on preexisting conditions means that most likely, health insurers could not use testing data to deny coverage or increase premiums.

But, she said, “there are some question marks around the discrimination risks.” This is especially true for people seeking long-term care, disability or life insurance, she added.

If a test result is not documented in a medical record, it’s not clear whether the individual has an obligation to disclose the result to an insurer, said Arias.

Given all the unanswered questions about how results should be interpreted, to whom the results should be disclosed, and when and how to have discussions with patients, “it’s hard for me to imagine that we’re quite ready for a direct-to-consumer” test, Arias said.

Mozersky noted that Washington University has a financial stake in C2N Diagnostics, which makes the PrecivityAD — biomarker tests for AD. Arias reported having no conflicts of interest.

Alicia Ault is a Saint Petersburg, Florida-based freelance journalist whose work has appeared in many health and science publications, including Smithsonian.com. You can find her on X @aliciaault and on Bluesky @aliciaault.bsky.social.