Health & Wellness

A New Blood Test for Alzheimer’s Disease

The promising new test may be able to detect Alzheimer’s 20 years before symptoms appear

By Caitlin Finlay


Alzheimer’s is a debilitating disease that over time affects memory, motor skills, and cognitive function. While there’s no cure yet, early treatment and lifestyle changes may slow the progression of the disease and preserve cognitive function for longer.

Now a large international study has shown that a new blood test—less expensive and less invasive than current diagnostic tools—can accurately distinguish between those who do and don’t have Alzheimer’s; it can also detect the disease in those with a known genetic risk. The study results were published July 29 in JAMA, the Journal of the American Medical Association.

Current methods for detecting or diagnosing Alzheimer’s are magnetic resonance imaging (MRI), positron-emission tomography (PET) scans, spinal fluid analysis from spinal taps, and confirming the diagnosis through an autopsy after the person has passed. Research has previously been conducted to find a blood test to detect amyloid proteins, which have been linked to Alzheimer’s disease, but the presence of amyloid proteins alone is not enough for a diagnosis. The new test can detect tau tangles, as well as amyloid proteins—a buildup of these tangles and proteins in the brain provides enough information for a diagnosis of Alzheimer’s disease. The accumulation of these tau tangles is also thought to be associated with the worsening of cognitive function.

The new blood test, which detects levels of a tau protein called p-tau217, was evaluated using three studies—in Arizona, Sweden, and Colombia—involving 1,402 research participants, including cognitively impaired and unimpaired participants. The p-tau217 test results were compared with those of other tests: biomarker blood tests, MRI scans, PET scans, and spinal fluid analysis. The p-tau217 test was able to detect Alzheimer’s as well as or better than the current methods, performing better than other blood tests and MRI scans, and as well as PET scans and spinal fluid biomarkers.

Checking p-tau217 levels by means of blood tests could also be a way to monitor those at high risk for Alzheimer’s. Levels of p-tau217 were seen to start increasing as early as 20 years prior to the age symptoms were predicted to appear. This finding could provide a way to track the progression of Alzheimer’s in those with and without cognitive effects.

Further testing will have to be done before the new blood test can be available to the public, but researchers are hopeful that it might be available within the next few years.

Photo: iStock/Kubra Cavus.