A new blood test may predict Alzheimer’s risk. It isn’t ready for prime time

A New Blood Test May Predict Alzheimer’s Risk Years Before Symptoms

A new blood test may predict who is at higher risk for Alzheimer’s disease, offering hope for earlier intervention. Researchers have discovered that elevated levels of a protein called p-tau217 in the blood can signal increased vulnerability to cognitive decline. According to recent findings, people without current memory problems but with higher p-tau217 concentrations face a significantly greater chance of developing early dementia signs. Over five years, those with elevated levels showed about 38 percent more likelihood of warning symptoms. The risk rose to 78 percent over ten years, though researchers acknowledge the longer-term data carries slightly less certainty.

Understanding How the Test Works

Traditionally, confirming Alzheimer’s required expensive and invasive procedures like PET scans and spinal taps to collect cerebrospinal fluid. The newer approach simply measures phosphorylated tau 217 levels in a standard blood draw. Lead researcher Rachel Buckley, associate professor of neurology at Harvard Medical School, explained that this biomarker “strongly predict[s]” the buildup of beta-amyloid plaques in brain tissue. These sticky deposits trigger inflammation and disrupt communication between nerve cells. Importantly, such accumulations can begin forming decades before noticeable memory problems appear, sometimes even in people in their thirties and forties.

“What this tells me is that we really can use p-tau217 blood tests in future to be able to understand somebody’s individual risk of cognitive impairment,” Buckley said.

As beta-amyloid builds up in brain structures, tau proteins start clustering inside neurons, eventually causing these cells to deteriorate and die. While certain conditions like frontal lobe dementia feature tau accumulation without amyloid, Buckley emphasized that elevated amyloid doesn’t guarantee dementia progression, just as tau presence alone doesn’t ensure future cognitive impairment. “However, if an early stage of tau is combined with very elevated levels of amyloid, amyloid appears to be the match that lights the fire for the spread of disease across the brain,” she noted. “What we think the p-tau217 test can show us is the moment when amyloid is starting to cause this sort of wildfire.”

Current Recommendations and Future Potential

Medical professionals currently recommend these assessments mainly for individuals showing mild cognitive impairment or more advanced dementia rather than completely healthy older adults. Buckley, who also investigates memory disorders at the Mass General Brigham Neuroscience Institute in Boston, expressed optimism about broader application. “Hopefully, p-tau217 tests can one day function like tests that measure your risk of developing diabetes or having a heart attack — but this test would be for your risk for Alzheimer’s disease and dementia,” she added.

Dr. Richard Isaacson, an Alzheimer’s prevention specialist at the Institute for Neurodegenerative Diseases in Florida, offered valuable perspective on proper test usage. He wasn’t involved in the primary study. “Never would I order a p-tau217 test in isolation. Why? For one, it tells you only one small part of what is most often a complicated biological picture,” Isaacson explained. He routinely cross-references p-tau217 findings with multiple blood and cognitive assessments to avoid false positives. “Also, ordering a single test increases the chance of a less meaningful result, like a false positive,” he cautioned. “If someone has a cold, if someone has kidney dysfunction, it can skew results.”

Rather than using p-tau217 and amyloid measurements exclusively for diagnosis, Isaacson employs them to monitor patient responses to therapies and lifestyle changes. “In our lab, we are exploring using these tests as a real-time metric, like an engine light,” Isaacson described. “If you have one or two copies of APOE4 and APOE4 protein levels are high, you can put the right fuel in the car — nutrition, exercise, stress management and the rest — and do preventive maintenance to lower your proteins.” Personalized lifestyle modifications including enhanced dietary habits, regular physical activity, quality sleep, increased social interaction, alongside management of insulin sensitivity, cholesterol levels, and additional risk factors have demonstrated measurable reductions in both amyloid and tau concentrations among committed patients.