A blood test being studied may soon be able to screen people for Alzheimer’s disease in its early stages. The ALZpath pTau217 assay would lead to a range of developments, including earlier and more precise Alzheimer’s disease diagnoses, improved patient management and timely access to disease-modifying therapies. 

The test seems to be faring better than a similar direct-to-consumer home blood test kit that hit the market last summer. The AD-Detect blood test by Quest Diagnostics was designed to assess a user’s risk for developing Alzheimer’s disease; however, experts soon raised concerns about the soundness of the research backing the test, its high rate of false positives and the potential for misuse of the results.

Here are some of the differences between the two tests, and what you need to know about the latest developments.


AD-Detect, the test from Quest Diagnostics, measures the level of a protein called beta-amyloid, a key component of plaques that form in the brains of Alzheimer’s disease patients, disrupting brain function. So the test doesn’t detect Alzheimer’s disease per se, but whether a person might have the building blocks necessary for developing similar pathology in their brains.

Researchers have raised several issues with AD-Detect. For one, it has not been evaluated nor approved by the FDA. According to one article from CNN, Quest hasn’t published any peer-reviewed studies to document the test’s validity. Additionally, preliminary data released in 2022 suggests that there’s a high chance of false-positive results. Experts are also concerned that the test could cause confusion in terms of diagnosis: A positive result — indicating abnormal levels of amyloid in the blood — doesn’t mean an individual will develop Alzheimer’s disease. It just indicates that the individual could get Alzheimer’s, but provides no insight into when symptoms could begin presenting, or really any degree of how high the risk would be.

In the same article, Rebecca Edelmayer, senior director of scientific engagement for the Alzheimer’s Association, cited her concern that a positive result from the AD-Detect test could cause a patient who has cognitive symptoms to ignore other possible causes and miss out on potentially effective care or treatment. Therefore, the Alzheimer’s Association does not endorse the use of the AD-Detect test by consumers, she said. 

ALZpath pTau217

This new study tests for a type of protein called phosphorylated tau, or more specifically in this case, p-tau217. People with Alzheimer’s experience an increase of p-tau217 along with other damaging proteins like beta-amyloid and tau in their brains. Up until now, it was necessary to get a brain scan or spinal tap for diagnosis. The new blood test, however, was found to be 96% accurate in identifying elevated levels of beta-amyloid and up to 97% accurate in identifying tau, according to a study published by the journal JAMA Neurology. It could eliminate the necessity of undergoing more costly or more invasive procedures.

The difference in experts’ confidence regarding the two tests has mostly to do with research that has been made available to the scientific community. The assay, developed by ALZpath, is a commercially available tool already being used in multiple labs around the globe. The p-tau217 test is currently available for research use only, but it is expected to be available for clinical use relatively soon. 

Not only is it hoped that this test could be used to provide an earlier and more precise Alheimer’s diagnosis, but it could lead to more targeted treatments as well. In the study, the test demonstrated “high accuracy” in identifying tau pathology in people who tested positive for beta-amyloid, which may help guide treatment decisions for patients considering therapies that target the latter, such as Leqembi and Aduhelm

Additionally, because the p-tau217 test is specific for Alzheimer’s disease, if someone tests negative while showing signs of cognitive impairment it could speed up the investigation for other causes of those symptoms, like vascular dementia or Lewy body dementia.

The Bottom Line

As of the writing of this article, there is no “magic bullet” for diagnosing diseases that cause cognitive decline, although new, promising options appear to be on the horizon.

If there is any concern that someone you love is demonstrating signs of cognitive impairment — confusion, memory loss, poor judgment, disorientation — the best thing to do is consult with their doctor. There are treatments available to slow some forms of dementia, as well as treatable medical conditions that could be causing the symptoms. The earlier you can get answers, the sooner you can implement a care plan. Furthermore, we heartily recommend reaching out to your local chapter of the Alzheimer’s Association, which will lend assistance regardless of an official diagnosis.

Top image by NoSystem images from Getty Images Signature, via Canva.com

More Articles Related to Alzheimer’s: