Blood Test Could Soon Accurately Diagnose Alzheimer’s in Those with Early Signs

Researchers have achieved a major advancement in diagnosing Alzheimer’s disease in individuals with mild cognitive decline by using a simple blood test with 90 percent accuracy.

The blood test, revealed in a new study funded in part by the National Institutes of Health (NIH), was significantly more accurate than cognitive tests, CT scans or invasive spinal taps in finding markers of Alzheimer’s, the most common form of dementia.

Currently, an accurate diagnosis of Alzheimer’s disease requires either a sample of cerebrospinal fluid or a brain imaging test called a PET scan. But neither of these tests can be done in primary care clinics, where most people with cognitive complaints are first seen, states the NIH.

G. Peter Gliebus, M.D., neurologist at Marcus Neuroscience Institute, part of Baptist Health, at Boca Raton Regional Hospital.

The new study, published in the journal JAMA, used a blood test that focuses on a form of a protein called tau that sprouts in the brains of people with Alzheimer’s. The blood test measures the ratio of two types of amyloid beta (a main component of the amyloid plaques found in the brains of those with Alzheimer's) as well as the proportion of tau.

Both measures were previously shown to predict a diagnosis of Alzheimer’s disease, explains G. Peter Gliebus, M.D., a neurologist with a subspecialty certification in behavioral neurology and neuropsychiatry, at Marcus Neuroscience Institute, part of Baptist Health, at Boca Raton Regional Hospital.  .

“What's unique about this test is that it measures the specific proteins that are associated with the disease process,” said Dr. Gliebus. “But it doesn't only measure the concentrations, it also expresses the specific ratios. And those ratios, or formulas, are what increases the accuracy of this test.”

Maria A. Vera Silva, M.D., a neurologist at Baptist Health Miami Neuroscience Institute, explains that the blood test is a potential breakthrough for patients with early signs of dementia who could benefit from various therapies to delay the full onset of Alzheimer’s.

Maria A. Vera Silva, M.D., neurologist at Baptist Health Miami Neuroscience Institute.

“This blood test is likely the beginning of more advances in the early diagnosis and treatment of Alzheimer’s, which is vital as the number of people living with the disease is growing substantially. This blood test is a definite milestone.”

The number of people beyond the age of 65 living with Alzheimer’s doubles every five years, according to the U.S. Centers for Disdease Control and Prevention (CDC). Currently, the disease affects an estimated seven million Americans. Dr. Gliebus stresses that the candidates for this blood test are individuals demonstrating mild cognitive issues, or early signs of Alzheimer’s, such as memory lapses and difficulties with some daily tasks.

“The appropriate patients would be the ones who have some complaints and also have some objectively measurable cognitive deficits,” said Dr. Gliebus. “This means it is not appropriate to use this test for people who are normal, or as screening tests. So, it’s for anybody who has mild complaints or mild cognitive impairment.”

In a news release, the NIH explains that the blood test performed far better than clinical evaluations done without biomarker-based testing. “Such clinical evaluations were 73 percent accurate at identifying Alzheimer’s disease when done in specialty memory clinics, and only 61 percent accurate when done in primary care settings,” the NIH said.

As more testing is undertaken and the blood test becomes widely available, it will eliminate existing “bottlenecks” that slow or prevent the diagnosis of Alzheimer’s disease, states the NIH. Not having an official diagnosis prevents people from receiving drugs that can slow the progression of Alzheimer’s. It also may allow these individuals to join clinical studies of new treatments.