New Research Suggests Simple Blood Test Could Most Accurately Detect Alzheimer's Disease

A simple blood test can accurately identify whether a person with memory issues has Alzheimer’s 91% of the time, making it significantly more accurate than traditional methods doctors use to assess and diagnose the disease.

The findings come from a new study, published July 28 in the journal JAMA and presented at the Alzheimer’s Association International Conference. and are the latest step forward in developing a cheaper and simpler test for a disease that affects nearly 7 million Americans.

“These findings may have major implications for all those individuals who seek help for memory loss and suspected Alzheimer’s,” Oskar Hansson, MD, PhD, professor of neurology, head of the clinical memory research unit at Lund University in Sweden, and an author of the study, told Health. 

Here’s what to know about what this new research might mean for Alzheimer’s diagnoses going forward.

For the new study, researchers looked at 1,213 patients in Sweden with an average age of 74. Throughout the study, the participants were experiencing mild memory symptoms, a potential early sign of Alzheimer’s.

Of these, 515 were evaluated in primary care and 698 in a specialist memory clinic. These patients were tested using the new blood test, and the test results were then confirmed with cerebrospinal fluid tests that can indicate Alzheimer’s disease.

Researchers measured the level of plasma phosphorylated tau 217 (p-tau217), a type of protein that builds up and impairs the brain in Alzheimer’s patients, and amyloid beta, another protein that is considered a biomarker of Alzheimer’s.

The blood test’s reliability of about 90% in identifying Alzheimer’s disease was compared with doctors’ assessments within primary or specialist care before they were allowed to see the results of the blood test or cerebrospinal fluid test.

Primary care doctors’ accuracy in identifying Alzheimer’s disease was 61%, while specialist physicians were correct 73% of the time.

Researchers said that the simplicity and reliability of this blood test make it a significant advancement in diagnosing Alzheimer’s, offering a straightforward method to rule out the disease in primary care, as opposed to more invasive blood tests and doctor visits that would require extensive screenings and tests. Because of the convenience of this test, diagnosing Alzheimer’s could be done more quickly and easily, allowing patients to develop a plan and better prepare for their future.

Researchers warned, however, that because this was conducted in Sweden, the results should be confirmed in a diverse American population and that the blood test should only be used for people who are already exhibiting symptoms of cognitive decline or memory loss. It should not be used to predict if a healthy person might develop Alzheimer’s.

“The next steps include establishing clear clinical guidelines for the blood test’s use in healthcare,” said Hansson. “The test is already available in the USA and is likely to become available in many other countries soon. Initially, it will mainly be used in specialist memory clinics, and it may take approximately one to two years to implement guidelines and training in primary care.”

Doctors currently use a combination of methods to test for Alzheimer’s disease as well as other potential causes of cognitive or behavioral changes that may indicate a neurodegenerative disease.

These methods typically include a detailed medical history, review of medications, family history, social history, comprehensive neurologic exam, varying degrees of neuropsychological testing, blood tests to assess for reversible causes of these changes, and brain imaging techniques like MRI scans.

In some cases, advanced imaging such as PET scans or spinal fluid tests to detect biomarkers like beta-amyloid and tau proteins are also used, but there is still a pressing need for simpler and quicker diagnostic tools for use in primary care, according to Hansson.

But while the new blood test is certainly groundbreaking, it’s not yet meant to be the only diagnostic method.

“The blood test described in the study is a promising development, but it is not yet a replacement for the current comprehensive diagnostic process,” Joel Salinas, MD, Clinical Assistant Professor of Neurology at NYU Grossman School of Medicine and founder and Chief Medical Officer at Isaac Health, told Health.

“It is beneficial because it can be less invasive and more accessible than spinal fluid tests,” Salinas said, adding that it can also “help to guide who would benefit most from advanced imaging studies to make the most judicious use of clinical resources.”

Additionally, the new test’s accuracy is highest in patients who have already progressed to dementia or mild cognitive impairment, and it is less accurate in the early stages of cognitive decline.

“While the blood test could serve as a helpful tool in conjunction with other diagnostic methods, further research is needed to establish clear guidelines for its use and to determine its role in improving treatment outcomes,” said Salinas.

Alzheimer’s disease affects one in five women and one in 10 men over their lifetimes, and its symptoms can go undetected for up to 20 years. Because of this, experts say that routine screening and more research are needed for early detection.

“The next step is for clinicians to create a pipeline for quick access to diagnosis and management of amnestic mild cognitive impairment and mild Alzheimer’s dementia,” Kaitlin Seibert, MD, an assistant professor of neurology at University of Chicago Medicine, told Health.

“Because amyloid protein can exist in the brain for years without causing any clinical symptoms at all,” Seibert added, “clinician assessment is integral to identify the right patients to undergo further testing based on their clinical syndrome.”