Researchers Identify a Promising Blood Test for Detecting Alzheimer’s Risk

New research is pointing to the likelihood of a commercially available blood test being used to accurately detect Alzheimer’s disease. The blood test is simple and could replace costly imaging tests that are currently used to confirm Alzheimer’s.

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By Alzheimer's Prevention Bulletin

Scientists are finding new ways to detect Alzheimer's disease earlier and more easily. One way they're exploring is through blood tests, which could make diagnosing and monitoring the disease simpler than current methods that involve complex brain scans or spinal fluid tests.

One test, called the plasma p-tau assay, shows significant promise. Tau is a protein that builds up in the brains of people with Alzheimer’s, and phosphorylated tau (p-tau) is a modified form of tau. Researchers have found that levels of phosphorylated tau in the blood tend to rise as Alzheimer’s gets worse. The promising results are highlighted in a January 2024 article published in JAMA Neurology.

“In research, we have known that a blood test for Alzheimer’s disease was possible but getting these tests reliable enough to be useful in ‘the real world,’ was the goal,” said study author Nicholas J. Ashton, PhD, Associate Professor, Senior Director of the Biomarker Program, Banner Sun Health Research Institute. “This study shows the first case of such a test being reliable, reproduceable and of high accuracy.”

Scientists performed and evaluated the blood test in three groups of people: those with no cognitive issues, those with mild cognitive impairment (MCI), and those with Alzheimer’s dementia. The blood test performed equally well in all, which is significant. “This means this test works well to identify Alzheimer’s pathology in asymptomatic stages as well as at mild stages and advanced stages,” said Ashton. He did caution, however, that the test should only be used in people who have symptoms currently and it should be guided by a health care professional.

What the study shows is that levels of p-tau in the blood increased as Alzheimer’s progressed. The highest levels were found in people who had both amyloid plaques and tau tangles in their brains, which are signs of Alzheimer’s. They used brain scans and spinal fluid tests to confirm the presence of Alzheimer’s pathology.

The study findings hold great significance, said Ashton. For patients with mild symptoms, it highlights quickly who might benefit from recently approved disease-modifying treatments. Also importantly, it highlights people whose symptoms are not caused by Alzheimer’s, and they can have more advanced tests for a more accurate diagnosis. In both cases, it drastically speeds up the patient management process.

Brain scans and spinal fluid tests are restrictive, costly, not widely available and do not allow for frequent testing. A blood test changes this completely, according to Ashton. He said the test is so simple that if cognitive decline is suspected the test would give valuable information. While training will be needed for providers to understand the test results, it’s likely testing would be centralized in a lab, such as Ashton’s new lab at Banner Sun Heath Research Institute. “The test does need to be taken in context of the individual patient, so it will support a clinical assessment rather than replace it,” he said.

What is on the horizon, following this important research finding? “In the future, we could potentially screen whole populations and administer treatment before symptoms,” said Ashton.

We expect that both the Alzheimer’s Prevention Registry and its GeneMatch program will have studies related to this topic in the coming months. Watch for study opportunity announcements and visit our Find a Study page. Not currently a member of GeneMatch? Click here to learn more and enroll.