A groundbreaking new study shows that soon there may be an accurate and easy-to-use blood test for Alzheimer’s disease. The test looks for biomarkers in the blood that are linked to the buildup of proteins that are linked to Alzheimer’s. This lets doctors find the disease years before any signs show up.
The study, which came out on January 22 in JAMA Neurology, found that measuring the amount of phosphorylated tau (p-tau) protein in the blood was a good way to find brain changes that are caused by Alzheimer’s.
Tau and another protein called beta-amyloid stick together in the brains of people with Alzheimer’s. This makes plaques and tangles that damage nerve cells and cause memory loss and dementia.
The study said that the blood test was “similar in diagnostic accuracy” to expensive PET brain scans and invasive lumbar punctures that are currently used to find early chemical signs of Alzheimer’s.
A blood test, on the other hand, looks like a cheap and painless way to screen a lot more people who are at risk than those other methods.
“This blood test shows very, very accurately who has Alzheimer’s disease in their brain, even in the early stages of the disease,” said Adam Boxer, MD, PhD, a neurologist at the UCSF Memory and Aging Center and co-author of the study.
“This is a very exciting discovery because it means we now have a biomarker blood test that can easily find the disease early.”
Blood Test Screens for Key Biomarker
The test looks for p-tau217, a tau protein that has been studied before and was found to highly associate with the formation of tau tangles in the brains of Alzheimer’s patients.
More than 1,400 adults aged 60 to 92 who were taking part in longitudinal aging studies at three university medical centers were tested for the p-tau217 blood biomarker.
Researchers found that p-tau217 levels correctly separated people with Alzheimer’s from healthy people, even when age and sex were taken into account. This was true for both people with and without dementia symptoms.
Unlike a different type of tau called p-tau181, p-tau217 levels were accurate indicators of the disease in people of all races and ethnicities.
Because of this, Dr. Boxer said, “the test may be especially useful for diagnosis in busy primary care settings, where clinical staff have limited time to spend on diagnostics and patients come from all walks of life.”
Test Could Expand Access to Early Alzheimer’s Detection
Both PET scans and cerebrospinal fluid taps showed the same level of sensitivity and specificity for the p-tau217 blood test. A PET scan can cost up to $5,000, and a lumbar puncture is an invasive process that many people would rather not have.
A blood test that is easy for many people to get could make early diagnosis easier for more people, giving doctors and patients a better chance to treat or slow Alzheimer’s sooner.
Maria Carrillo, PhD, Chief Science Officer for the Alzheimer’s Association, said, “An Alzheimer’s blood test also promises to test a lot more people.” “More primary care doctors could easily order a blood test for their patients than could easily send them to a neurosurgeon for a PET scan.”
The Alzheimer’s Association says that more than 6 million Americans aged 65 and up have the disease. Alzheimer’s has no known cure, but early intervention may help keep people’s quality of life and slow down cognitive loss before damage is done that can’t be fixed.
There may not be much time for the best therapeutic approaches once symptoms show up, Dr. Carrillo said. “That’s why scientists are looking for and validating biomarkers, such as blood tests, that could help find the disease earlier.”
Additional Validation of Test Accuracy Still Needed
Before blood-based screens are approved for clinical diagnostic use, the study authors said that the high accuracy of p-tau217 testing needs to be proven in bigger, more diverse patient samples.
“It will be important to look at how well these blood tests work, including how sensitive and specific they are, in community settings where people are different in age, race, ethnicity, disease stages, and maybe even other things,” Dr. Boxer said.
Still, this new study gives us new hope that using slightly invasive blood sampling to find Alzheimer’s early could soon be used outside of research labs and during regular doctor visits.
And because Alzheimer’s is a disease that gets worse over time, a test that can properly find the disease before symptoms show up and bring patients in for care could have a huge effect.
Dr. Carrillo said, “This extra tool for early detection can make it possible for more people to benefit from the dementia-focused interventions that are already happening.” “And it will speed up drug trials so that people who need new treatments can get them faster.”