Will Doctors Use a New Blood Test for Alzheimer's?

Alzheimer’s disease can only be definitively diagnosed after death, leading doctors to make a presumed diagnosis while a patient is still alive. But a large team of researchers recently developed a blood test that can diagnose the disease with up to 96% accuracy.

Details about the blood test, which is not yet ready for clinical use, were published in JAMA in late July. In their study, the researchers detail how they use the protein p-tau217 to differentiate Alzheimer's disease from other neurodegenerative diseases through a simple, low-cost blood test. The study analyzed data from 1,402 patients and found that the new blood test had “significantly higher accuracy” than more established tests like plasma- and MRI-based biomarkers.

“I hope that in two to three years’ time, a blood test for Alzheimer’s disease can be used in clinical practice to improve diagnostics and thereby treatment and care of patients with Alzheimer’s,” study co-author Oskar Hansson, MD, PhD, a neurologist and head of the Clinical Memory Research Unit at Sweden’s Lund University, tells Verywell.

The Use Case For a Diagnostic Test

Alzheimer’s disease has minimal treatment options. Currently, patients with mild to moderate Alzheimer’s may be prescribed medications called cholinesterase inhibitors to try to help reduce some symptoms, but the medication loses its effectiveness over time, according to the National Institute on Aging (NIA).

Patients with moderate to severe forms of the disease may be prescribed different medications, including memantine, allowing them to keep certain daily functions a little longer than they would without medication, the NIA says. Still, none of these treatments are perfect and there is currently no treatment that can cure or halt the progression of the disease.

Knowing that they could potentially diagnose Alzheimer's—but sill not cure it—would doctors actually use this test if it were available today? The answer appears to be yes, as long as it is used to diagnose Alzheimer's in symptomatic patients, not screen for it.

"A blood marker for Alzheimer’s would be get used all the time if it was specific for the disease," Amit Sachdev, MD, director of the Division of Neuromuscular Medicine at Michigan State University, tells Verywell.

For starters, a diagnosis could help empower people who are beginning to develop symptoms of Alzheimer’s disease, such as memory loss and confusion.

Detecting the disease early can help patients to be “more involved in discussions regarding diagnosis, prognosis, and treatment options, and to be involved in making medical, financial, and legal plans for the future,” says Verna Porter, MD, a neurologist and director of the Dementia, Alzheimer’s Disease, and Neurocognitive Disorders at the Pacific Neuroscience Institute at Providence Saint John’s Health Center.

A diagnostic test can also help doctors make better decisions around medications.

“My goal is to max out medications as much as tolerated,” Kinga Szigeti, MD, PhD, director of the University at Buffalo’s Alzheimer’s Disease and Memory Disorders Center, tells Verywell. “If I’m second-guessing my diagnosis, I might stop the medication if there are concerns about side effects. But, if I’m certain of the diagnosis, I would be more aggressive with treatment and try different strategies.”

Doctors Warn Against Using This Test as a Screening Method

While it seems like this new blood test could be used as a screening method to help people know if they are at high risk of developing Alzheimer’s disease in the future, Hansson cautions against using the test that way.

“In clinical practice, the test should only be used in patients with significant cognitive symptoms, where the responsible physician thinks it is of value for the patient to get an accurate diagnosis,” he says. “We do not advocate to use the test to screen healthy populations for Alzheimer’s disease, with the exception when identifying individuals with very early Alzheimer’s disease for clinical trials evaluating novel therapies that might slow down or even stop the disease.”

Telling someone with no symptoms that they’re likely to develop Alzheimer’s disease at an indeterminate time “just increases anxiety and worry,” Szigeti says, explaining she would not use the test as a screening tool.

Added Benefits of the Blood Test

MRIs and other Alzheimer’s diagnostic tests can be pricey. “This test can improve diagnostic accuracy in an inexpensive way,” Szigeti says. She adds it may also help bring peace of mind to people who are worried that they may be developing Alzheimer’s disease, but are actually experiencing symptoms due to another health issue.

The blood test may also help identify people who qualify for clinical trials.

"Those trials use medications that we are hoping will stop the progression of the disease, and may be more helpful for certain patients,” Szigeti says.

Ultimately, the test may be more helpful with time as new treatments are developed.

“With an increasing focus on prevention in developing new medications, the potential for intervening early will become very important over the next years,” Paul Newhouse, MD, director of the Vanderbilt Center for Cognitive Medicine, tells Verywell. "We have been searching for some time for blood tests that would help us confirm the diagnosis of Alzheimer's disease. If these results are confirmed, this could be a very promising new diagnostic test that would help us diagnose patients earlier than we are able to now."