The first direct-to-consumer Alzheimer’s disease blood test has arrived. Quest Diagnostics, a worldwide diagnostic service headquartered in Secaucus, New Jersey, announced on July 31 that it would market a plasma Aβ42/ Aβ40 Alzheimer’s test to the public.

  • Quest Diagnostics is selling an AD blood test directly to consumers.
  • No peer-reviewed data are published on the test.
  • It has low specificity, potentially generating many false-positive results.
  • Experts fear it will do more harm than good.

The “AD-Detect Test” is available on the Quest website for $399 to anyone over 18. After going in for a blood draw at a Quest clinic, purchasers will receive a digital report with the results, and be offered the chance to discuss them via telemedicine with an “independent physician.” The assay uses a mass-spectrometry methodology similar to blood tests developed at Washington University in St. Louis. Unlike those tests, however, there are no published data on how Quest's test performs, nor on how it was validated.

Alzheimer’s researchers contacted by Alzforum universally decried Quest's decision. In addition to concerns about the test’s accuracy, they stressed the need for blood tests to be interpreted by a knowledgeable dementia specialist. “This is clearly not a good idea," Philip Scheltens, who last month retired from VU University, Amsterdam, wrote to Alzforum. “Every diagnostic test should be used in the context of a proper workup led by a skilled clinician,” he added (comment below). Scheltens now heads EQT Life Sciences Dementia Fund.

Suzanne Schindler at WashU noted that people tend to trust blood tests, and likely will not understand the uncertainty and nuances of being amyloid-positive or -negative. “People will think they have a clear answer, when they do not,” Schindler told Alzforum. More broadly, lack of clear standards and regulations, combined with high demand, could lead to many poorly validated tests coming on the market.

Scientists have been working on AD blood tests for many years, and the topic took on new urgency after the Food and Drug Administration approved the amyloid immunotherapy lecanemab (Jul 2023 news). More than a dozen such tests are in development at different companies (Hampel et al., 2023). So far, none are FDA-approved.

However, diagnostic tests do not need FDA approval to be marketed to the public. They can clear a lower bar by becoming CLIA-approved, meaning the assay has good test-retest reproducibility. Quest's test cleared this hurdle, but Alzheimer’s researchers are troubled by the lack of information about it. The only publicly available data come from a poster at the 2022 AAIC. In a cohort of 209 people, the test was reported to have a sensitivity of 0.89, specificity of 0.71, and AUC of 0.82.

AD researchers said this is not good enough for a consumer test. Such a test should have greater than 90 percent sensitivity and specificity, said Oskar Hansson at Lund University, Sweden (comment below). Henrik Zetterberg at the University of Gothenburg, Sweden, cautioned that the range of Aβ ratios for amyloid-positive and -negative people overlap significantly. “A direct-to-consumer test has to be super robust and easy to interpret. This is not the case for the plasma Aβ42/Aβ40 ratio, irrespective of which assay is used. The test needs to be interpreted together with additional biomarkers,” he wrote.

For comparison, the company C2N Diagnostics also sells a CLIA-approved mass spec plasma test using the Aβ42/Aβ40 ratio, but their test has extensive development and validation data behind it, and the company is not marketing directly to consumers.

How well would Quest's AD-Detect Test work in practice? If it were used in a memory clinic population, where 60 percent of patients have amyloid plaques, it would misdiagnose 18 percent of them, Schindler said (Rabinovici et al., 2019). However, the test is likely to reach a broader population, including cognitively healthy people concerned about their cognition.

The company’s website suggests its use for “anyone with a family history of Alzheimer’s disease” who is over 50. In this population, where 20 percent of people have amyloid plaques, the test would misdiagnose a quarter of them, Schindler calculated based on a recent study (Jansen et al., 2022). In particular, only 43 percent of positive results would be true positives. Earlier this month, Quest's website had recommended women take the test regardless of age or family history, but as of August 30, that sentence was no longer there.

Such a large number of false-positive test results would hike demand for follow-up testing and services from memory clinics. This would likely overwhelm them, noted Dennis Selkoe at Brigham and Women’s Hospital, Boston (comment below).

In the absence of expert guidance, misleading results could be severely distressing. “In our clinic, we see people in person to discuss a life-changing diagnosis such as Alzheimer’s disease,” Andrew Budson at the VA Boston Healthcare System wrote to Alzforum. Budson thinks blood tests are the future but that little good will come of direct-to-consumer testing.

Scientists noted many downsides. For one, a cognitively healthy person with a positive test would not qualify for treatment with lecanemab, and insurance would likely not cover follow-up testing. For another, positive tests could discourage people from investigating other, treatable, causes for their cognitive problems, such as medication side effects or depression, said Michelle Mielke at Wake Forest University in Winston-Salem, North Carolina. Charlotte Teunissen at Amsterdam UMC fears that inaccurate results will lead people to lose faith in AD blood testing. Teunissen cited the Dutch saying, “Trust arrives on foot, but leaves on horseback.”

Mielke and Teunissen are among the world's leading AD fluid biomarker experts. Both are working closely together, with Schindler, Hansson, and many others, in an ongoing effort started by Kaj Blennow, Henrik Zetterberg, and Maria Carrillo in 2011 (Aug 2012 conference news). Called the Global Biomarker Standardization Consortium, aka GBSC, these scientists work to ensure that CSF and blood tests are being properly developed, validated, and fully certified by their respective country's clinical chemistry agencies, such that they can be robust and trustworthy once they enter prime time (e.g. Blennow Q&A; see also Further Reading below and GBSC webpage).

In 2022, the Alzheimer’s Association published appropriate-use recommendations for blood-based biomarkers. They suggest that, for the time being, these tests be used only in specialty clinics, with positive results confirmed by CSF or amyloid PET (Aug 2022 news). Ultimately, FDA approval will be needed to define a gold-standard test, Schindler said. She predicted that the longer this takes, the more chaotic the arena will become in the interim.—Madolyn Bowman Rogers


  1. This is clearly not a good idea. Aside from a far from satisfactory sensitivity and specificity, which leaves far too much room for false-negative and false-positive results, it is also in contrast to what the AD community has always voiced very clearly: every diagnostic test should be used in the context of a proper work-up led by a skilled clinician.

    The people who likely seek comfort in ordering such a test are the so-called "worried well," people who experience memory problems and worry about incipient Alzheimer's disease. More than one out of 10 of them will be reassured, falsely, that AD is not present, while an even larger percentage will be falsely suspected of AD. This will increase the burden on the healthcare system, which is already challenged by an increase in patients who want to know whether they are eligible for Leqembi.

    In a proper diagnostic workup, especially in those individuals without dementia, the diagnostic test results need to be discussed in the context of all other findings, and the diagnostic and prognostic value need to be intensely discussed. In a recent paper, Jetske van de Schaar et al. performed a meta-analysis of five studies, including 2,012 participants of whom 66 percent had elevated amyloid levels indicative of AD and 92 percent were asymptomatic. Based on the available empirical data on the impact of sharing results, these authors found that interest among personal stakeholders was high, and sharing test results did not cause significant short-term psychological harm, yet offered actionability. Although most healthcare professionals valued biomarker testing, attitudes and practices varied considerably. Their results indicate that even in a professional setting, development and harmonization of testing guidelines and communication protocols are required (van der Schaar et al., 2023). 


    . Impact of sharing Alzheimer's disease biomarkers with individuals without dementia: A systematic review and meta-analysis of empirical data. Alzheimers Dement. 2023 Dec;19(12):5773-5794. Epub 2023 Jul 26 PubMed.

  2. I am generally against screening of healthy populations, unless rigorous science has shown that such screening approaches result in more good than harm. To do that, large-scale, population-based prospective studies are needed. Such studies should show that the test used for screening must be very accurate (sensitivity and specificity likely well above 90 percent). That is because the pretest probability of AD will be rather low in the general population, resulting in many false-positive test results.

    There must also be a plan in place to detect false-positive results with another test (e.g., amyloid PET), and the costs for society to do that must be reasonable. Most importantly, a true, positive test result must be associated with the possibility to initiate a beneficial treatment in all individuals who have received such a result. This is why clinical assessments before testing are vital.

  3. I am against offering a direct-to-consumer Aβ42/40 blood test for individuals to initiate themselves without oversight by an experienced AD provider, who has formally evaluated the person for AD and other potential neurological conditions in several standard ways.

    Among several problems with the use of such a consumer-initiated test are the imperfect sensitivity, specificity, and AUC cited by Quest, a lack of an expert provider’s guidance about whether to obtain this test, and the lack of expert interpretation of the result in the context of the subject’s fully documented medical situation. This is a bad idea because it is prone to excessive ordering of a test that would be medically meaningless for many of those who choose to order it by themselves, including many people younger than 50, those with exclusionary medical conditions for AD treatment, and those without evidence of a cognitive syndrome consistent with AD.

    Moreover, the claim by Quest that this test could enable earlier access to a disease-modifying, amyloid-lowering therapeutic is highly misleading, because there are strict, detailed, prescribing guidelines as to which patients with definite signs of early AD should be considered for treatment with lecanemab, the only anti-Aβ antibody treatment fully approved by FDA at present.

    Further, the AD medical field is already concerned about the lack of sufficient capacity as regards expert providers familiar with this new class of treatments, and the use of this “over-the-counter” blood test could lead to many inappropriate subjects coming forward for evaluation of possible AD in a way that may well decrease the access for neurologically appropriate MCI/mild AD patients qualified for lecanemab and for other subsequently approved amyloid-lowering therapeutics. There are also economic arguments against widespread use of an imperfect, self-initiated blood test without full expert guidance on a personal basis.

  4. That this test is being marketed directly to consumers tells us that people are worried about Alzheimer’s disease, and that they don’t always want to work through their regular doctor. This is complicated by the fact that many primary care doctors aren’t knowledgeable about the latest biomarkers or treatments for Alzheimer’s, and by the wait to see dementia specialists being often six months or longer. I do think that blood tests to diagnose Alzheimer’s disease are the future, but I worry that the way Quest is going about it is a huge mistake, for two reasons.

    First, as many people have pointed out, the sensitivity isn’t so bad at 89 percent, but the specificity, at 71 percent, is terrible, meaning that a lot of people will be told that the biomarker suggests they have Alzheimer’s disease when they do not.

    Second, in our clinic, we don’t give amyloid or tau biomarker results back over the phone—we see people in person to discuss a life-changing diagnosis such as Alzheimer’s disease. I cannot imagine any good that will come of someone finding out that they are likely to have Alzheimer’s disease and then, at some time later, needing to seek out a doctor who can help them understand what the test means and what they should do about it.

    The bottom line is that, like it or not, primary-care physicians will need to become knowledgeable about Alzheimer’s disease and its biomarkers. There simply aren’t enough specialists out there to evaluate all the older individuals at risk for this disease. Blood tests for Alzheimer’s are the future, but they should be done through one’s doctor, and with a test that has higher sensitivity and specificity.

  5. This is a very worrying development, and may harm the process of implementation of blood-based biomarkers. As the Dutch saying goes, “Trust arrives on foot, but leaves on horseback.”

    The lack of any data is a very serious problem. Even if the assay is similar to C2N’s, that does not imply the same performance characteristics. Not all mass spectrometry assays have the same discriminative value, or correlate well with each other. See the global Alzheimer’s Association round robin study on plasma Aβ methods (Panee et al., 2021). 

    First of all, data should be disclosed. Did they test prospectively in real-world settings? And in the wider/general population, which they seem to target? Which reference standard was used for evaluation? These are only a few of the questions to address.

    Data shown by others, repeatedly, have indicated that only a 10-15 percent reduction in plasma amyloid ratios is observed in those who are amyloid-positive on a group level, and in the earlier stages of disease this difference might be smaller even. Therefore, assays must be of extremely high quality to perform well for individual patients. As long as Quest fails to disclose its data, testing cannot be done with this assay.

    Next, Alzheimer’s biomarker testing should always be done in the clinical context, taking the patient history into account and the evaluation of their cognitive performance by healthcare professionals.

    I am concerned this commercially driven announcement by Quest will lead to people obtaining a blood test result that they cannot interpret or contextualize themselves. They will likely seek medical advice, which will lead to an overload of the healthcare system.


    . The global Alzheimer's Association round robin study on plasma amyloid β methods. Alzheimers Dement (Amst). 2021;13(1):e12242. Epub 2021 Oct 14 PubMed.

  6. I do have several concerns about the Quest direct-to-consumer test. Below are just some of them.

    First, there is no published data on the test’s performance or how the cutoffs were determined. Other blood tests that are currently clinically available, albeit not FDA-approved, have been rigorously researched and the results presented to the public, and for peer review. It cannot be assumed that Quest’s test has good accuracy just because it is mass-spec based, which is similar to WashU’s test methodology.

    Second, current guidelines for the use of Alzheimer’s disease blood-based biomarkers recommend them for symptomatic individuals to aid in the diagnosis of Alzheimer’s—it is advised that AD blood tests not be used for asymptomatic individuals until more information regarding their prognostic ability can be obtained. The field is currently trying to understand how to best implement blood markers in primary care for the diagnosis of AD in symptomatic individuals.

    Moreover, an individual’s perceived cognitive change could be due to a variety of reasons, some of which are modifiable, e.g. medications, chronic conditions, depression, and a positive test result in these individuals could be incidental. Thus, AD blood tests should not currently be used in asymptomatic individuals only, under a physician’s guidance, for those with objective cognition changes that may be due to AD.

    Lastly, if this test is going to be available direct-to-consumer in the general population, then a rigorous assessment of this test in a diverse population-based cohort is necessary first.

  7. As an ApoE 4 homozygote, who discovered her genetic status though a NIH-funded study without counseling and experienced the following PTSD and suicide ideation that almost ended my life, I find this horrific. I can buy this test with little oversight. Where is the robust informed consent? Where is the FDA to protect humankind?

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Therapeutics Citations

  1. Leqembi

News Citations

  1. FDA Grants Traditional Approval to Leqembi
  2. CSF Markers: Goodbye, Research Use Only; Hello, Clinical
  3. Why Bother With Round Robins on Blood Tests? Q&A with Kaj Blennow
  4. Alzheimer's Blood Tests Have Arrived; Road to Broad Use Still Stretches On

Paper Citations

  1. . Blood-based biomarkers for Alzheimer's disease: Current state and future use in a transformed global healthcare landscape. Neuron. 2023 Sep 20;111(18):2781-2799. Epub 2023 Jun 8 PubMed.
  2. . Association of Amyloid Positron Emission Tomography With Subsequent Change in Clinical Management Among Medicare Beneficiaries With Mild Cognitive Impairment or Dementia. JAMA. 2019 Apr 2;321(13):1286-1294. PubMed.
  3. . Prevalence Estimates of Amyloid Abnormality Across the Alzheimer Disease Clinical Spectrum. JAMA Neurol. 2022 Mar 1;79(3):228-243. PubMed.

External Citations

  1. announced
  2. GBSC webpage

Further Reading