Blood test boosts Alzheimer's diagnosis accuracy to 94.5%, clinical study shows

A protein lurking around in the blood can help with the accurate diagnosis of Alzheimer's disease. In a recent study, researchers from Spain investigated how blood-based biomarkers, such as a protein called p-tau217, affect both the clinical diagnosis of Alzheimer's and neurologists' confidence in their diagnosis.

After following 200 consecutive new patients aged 50 and older who presented with cognitive symptoms, they found that a simple blood test measuring p-tau217 significantly improved diagnostic accuracy in routine clinical practice.

When relying solely on standard clinical evaluation, doctors correctly diagnosed Alzheimer's in 75.5% of cases, but when incorporating blood test results, diagnostic accuracy increased to 94.5%. The findings are published in the Journal of Neurology.

Better path to Alzheimer's diagnosis

Phosphorylated tau, or p-tau217, is a protein that naturally occurs in the brain and helps keep neurons, the cells that carry signals, stable and healthy. The trouble begins when this protein becomes abnormally phosphorylated and clumps together, forming tangles that disrupt communication between brain cells. Over time, this damage can impact brain function and lead to neurodegenerative conditions such as Alzheimer's disease.

While p-tau217 is not considered the direct cause of Alzheimer's, elevated levels in the blood are now recognized as one of the most accurate early warning signs of the disease.

In many parts of the world, the population is rapidly aging and so is the number of age-related diseases like Alzheimer's and dementia. However, most of the standard ways to diagnose Alzheimer's today, like expensive brain scans or invasive spinal taps, are costly, uncomfortable, and often hard for patients to access.

Scientists have long known that p-tau217 is a reliable biomarker for detecting early signs of Alzheimer's, but most of these data come from highly controlled research labs. How well it works in everyday medical clinics and whether it truly boosts doctors' confidence in their diagnoses remain less explored.

In this study, the researchers focused on both these factors in real-world medical settings. They followed patients who came in for general neurology consultations and to a specialized cognitive neurology unit with cognitive symptoms. Clinicians noted their initial diagnosis and how confident they felt about it, then reviewed the p-tau217 blood test results and recorded any changes.

The team found that after reviewing the p-tau217 results, diagnostic accuracy jumped by 19%. For about one in four patients, the blood test prompted doctors to change their diagnosis. Some people who were first believed to have Alzheimer's turned out to have a different condition, while others who were thought to be experiencing normal aging were correctly identified as having Alzheimer's. Also, the doctors' confidence in their diagnoses rose from an average of 6.90 to 8.49 on a 10-point scale.

The p-tau217 tests proved to be effective across every stage of cognitive decline, be it early memory complaints or late-stage decline such as dementia. The findings show that this blood test could provide a more accurate and less invasive way to diagnose Alzheimer's, potentially improving care for millions of people.

Written for you by our author Sanjukta Mondal, edited by Gaby Clark, and fact-checked and reviewed by Robert Egan—this article is the result of careful human work. We rely on readers like you to keep independent science journalism alive. If this reporting matters to you, please consider a donation (especially monthly). You'll get an ad-free account as a thank-you.

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