Scientists have been searching for better ways to detect Alzheimer’s disease (AD) early. One promising approach has been measuring levels of certain proteins, called p-tau 181 and p-tau 217, in the spinal fluid. High levels of these proteins are linked to Alzheimer’s, but the test requires a lumbar puncture, which can be painful and invasive.
Recent advances in blood testing have made it possible to detect these proteins without needing a spinal tap. Experts hoped this would make Alzheimer’s screening easier, cheaper, and more accessible to the general population.
However, a new study has revealed an unexpected complication: p-tau proteins in the blood are not as specific to Alzheimer’s as scientists once thought.
Surprising Discovery in ALS Patients
A team of researchers, led by Professor Markus Otto from University Medicine Halle, was investigating ways to detect neurological diseases earlier, including Alzheimer’s and ALS (amyotrophic lateral sclerosis). ALS is a severe disease that affects nerve cells controlling movement.
In their study, researchers analyzed blood samples from 111 Alzheimer’s patients, 152 ALS patients, and 122 healthy individuals. Their goal was to see if p-tau proteins could serve as a reliable early detection marker. The results, published in Nature Communications, surprised them.
The researchers found that ALS patients had high levels of p-tau 181 and p-tau 217 in their blood—just as high as Alzheimer’s patients. But unlike in Alzheimer’s, these proteins were not elevated in the cerebrospinal fluid of ALS patients. This suggests that blood tests for Alzheimer’s may not be as accurate as previously thought because they could also indicate ALS.
What This Means for Diagnosis
This discovery challenges the idea that p-tau proteins in the blood come only from the brain. In fact, further tests showed that muscle tissue in ALS patients can produce p-tau proteins. This suggests that other conditions, especially neuromuscular diseases, could affect p-tau levels in ways we don’t yet fully understand.
At first, this might seem like bad news for Alzheimer’s testing, but the findings open up new possibilities. Instead of being a setback, they could actually help in diagnosing and monitoring ALS. If p-tau levels in the blood are linked to ALS, these tests might be useful for tracking how the disease progresses and whether treatments are working.
For Alzheimer’s, blood tests for p-tau are still useful, but they should not be the only method for diagnosis. A positive test result should lead doctors to perform more thorough evaluations, such as memory tests, brain scans, or spinal fluid analysis, to confirm the diagnosis.
Because p-tau levels overlap between Alzheimer’s and ALS, using these tests alone for large-scale screening may not be reliable.
Why This Research Matters
With new Alzheimer’s treatments, like antibody therapies, already approved in the U.S. and expected in Europe, early diagnosis is more important than ever. But these findings show that scientists still have much to learn about p-tau proteins and where they come from.
The idea that these proteins come only from the brain is now being questioned. Researchers will need to explore how different tissues in the body contribute to p-tau levels and what this means for diseases like Alzheimer’s and ALS.
This study is a reminder that science is constantly evolving. What seems like a simple breakthrough—a blood test for Alzheimer’s—turns out to be more complex. But by learning more about p-tau, researchers may find new ways to diagnose, treat, and understand both Alzheimer’s and ALS in the future.
The research findings can be found in Nature Communications.
Copyright © 2025 Knowridge Science Report. All rights reserved.
