Progressing towards a tau blood test for Alzheimer’s disease

Researchers from both the US and Europe have presented data that indicates levels of a specific form of tau, one of the hallmark proteins of Alzheimer’s disease, can be measured in blood to detect the disease, even before symptoms appear. The findings have been presented today (July 28).

 

Increasing levels of tau in the blood can be detected up to 20 years before symptoms appear 

Research presented from scientists in Sweden showed that levels of p-tau217 in the blood reflected the levels of tau seen in state-of-the-art PET brain scans and could differentiate between people living with Alzheimer’s and those with other diseases that cause dementia.  

They found that changes in blood tau levels could be detected before symptoms of Alzheimer’s disease appeared. In a small subgroup of people these changes could be seen 20 years prior to the estimated onset of disease. The researchers also compared p-tau217 to a separate tau marker in blood, p-tau181, and showed that p-tau217 consistently outperformed p-tau181. 

In a second part of the study, also presented on Tuesday, increasing levels of p-tau217 were shown to be detectable in blood prior to the protein being visible in brain scans. These measurements were then able to be used to predict changes in tau in the brain as well as the development of Alzheimer’s disease.  

Levels of tau in the blood also track well with levels of amyloid in the brain

In a separate study, scientists from Washington University have shown that p-tau217 in the blood can also predict levels of amyloid, another hallmark protein of Alzheimer’s disease, in the brain. They also show that p-tau217 in blood can be used to identify different clinical stages of Alzheimer’s both before symptoms appear and as the disease progresses.  

P-tau217 performs well as a diagnostic tool for Alzheimer’s disease

In a final study, presented by scientists from San Francisco, a p-tau217 blood test was shown to perform as well as expensive PET brain scans for Alzheimer’s disease diagnosis. The test was also comparable to other blood markers when distinguishing between Alzheimer’s disease and a different neurodegenerative disease known as frontotemporal dementia.  

 Expert comment on the findings.

Dr Rosa Sancho, Head of Research at Alzheimer’s Research UK said:
“We know that brain changes in Alzheimer’s disease can occur decades before symptoms start to show and the early stages of disease are likely to be the time when future drugs are most effective.

“These studies suggest that changes in levels of a specific form of tau, one of the hallmark proteins of Alzheimer’s, may be detectable in the blood in the very early stages of the disease. The research also indicates that the changes seen in blood track protein build-up measured by brain scans.

“The tests can discriminate Alzheimer’s from other diseases that cause dementia, however, these findings are from small scale and early-stage research studies. Further work will need to be carried out at a larger scale and with tests that are clinically feasible before they could be used by doctors making a diagnosis in the clinic.

“Currently people only receive an Alzheimer’s diagnosis once symptoms appear. Many of the diagnostic tools that can detect early changes are expensive, like brain scans, or invasive such as spinal fluid tests. A reliable blood test for Alzheimer’s disease would be a huge boost for dementia research, allowing scientists to test treatments at a much earlier stage which in turn could lead to a breakthrough for those living with dementia.