With blood tests to diagnose and stage the disease, doctors could tailor treatments to each patient’s particular condition.
A blood test diagnoses Alzheimer’s and measures the degree of dementia. It was developed by a team of researchers from Washington University School of Medicine in St. Louis (USA) and Lund University (Sweden).
The new test can also provide information about whether a person’s symptoms are likely due to Alzheimer’s or another cause.
The study, published in the journal Nature Medicine , shows that the level of the MTBR-tau243 protein in the blood accurately reflects tau accumulation in the brain and the severity of the disease.
Currently, there are blood tests available to diagnose Alzheimer’s, but most do not provide information about the clinical stage of the disease. Since available treatments are most effective in the early stages, having an accessible and reliable method to assess the progression of the disease could help determine which patients would benefit most from available therapies.
The study analyzed blood samples from patients with varying degrees of cognitive impairment and demonstrated that the MTBR-tau243 level can distinguish between early and advanced Alzheimer’s disease, as well as differentiate the disease from other forms of dementia. With an accuracy of 92%, the test offers a more accessible and less invasive alternative to current positron emission tomography (PET) brain scans .
“This blood test clearly identifies Alzheimer’s tau tangles, which is our best biomarker for measuring Alzheimer’s and dementia symptoms ,” said co-senior author Randall J. Bateman . “ In current clinical practice, we don’t have easy or accessible methods to measure Alzheimer’s and dementia tangles, so a blood test for tangles like this can provide a much more accurate indication of whether symptoms are due to Alzheimer’s and may also help doctors decide which treatments are most appropriate for their patients.”
Alzheimer’s disease involves the buildup of a protein called amyloid in brain plaques, followed by the development of tau protein tangles years later . Cognitive symptoms appear around the time the tau tangles become detectable and worsen as they spread. The gold standard for staging Alzheimer’s disease is positron emission tomography (PET) scanning of the brain for amyloid plaques and tau tangles. Amyloid scans provide information about the presymptomatic and early symptomatic stages, while tau scans are useful for monitoring later stages of the disease. PET brain scans are highly accurate but expensive, time-consuming, and often unavailable outside major research centers, so their use is not widespread.
In a previous study, Bateman and his team showed that levels of MTBR-tau243 in cerebrospinal fluid closely correlate with tau tangles in the brain . In the current study, the team extended the analysis to blood. A blood sample is easier to collect than cerebrospinal fluid, which is obtained by lumbar puncture .
The researchers developed a technique to measure MTBR-tau243 levels in the blood and compared it to the number of tau tangles in the brain, as measured by brain scans. They implemented the approach using data from two cohorts: volunteers from WashU Medicine’s Charles F. and Joanne Knight Alzheimer’s Disease Research Center , which included 108 people, and a 55-person subset of the Swedish BioFINDER-2 cohort. To assess the approach’s generalizability, they validated it on an independent dataset composed of the remaining 739 people in the BioFINDER-2 cohort.
People in both cohorts represented all groups except the most severe end of the Alzheimer’s disease spectrum, from the presymptomatic stage, when brain amyloid levels are elevated but people remain cognitively healthy, through early-stage mild cognitive impairment, to late-stage symptomatic disease, when patients present with advanced dementia. For comparison, cognitively healthy people with normal amyloid levels and people with cognitive symptoms due to conditions other than Alzheimer’s disease were included .
The study revealed that MTBR-tau243 blood levels accurately reflect the accumulation of tau tangles in the brain with 92%. In asymptomatic individuals, these levels remained normal, even in those with amyloid plaques, indicating that they do not vary in the presymptomatic stage of Alzheimer’s. However, in patients with cognitive symptoms due to Alzheimer’s, MTBR-tau243 levels were markedly elevated in the mild cognitive impairment stage and up to 200 times higher in the advanced dementia stage. These differences allowed a clear distinction between the early and late stages of the disease. Furthermore, MTBR-tau243 levels remained normal in people with cognitive symptoms caused by other diseases, demonstrating that the test can effectively differentiate Alzheimer’s dementia from other types of dementia.
When both biomarkers are positive, the likelihood that Alzheimer’s is the underlying cause of cognitive symptoms increases significantly.
“We will use p-tau217 in blood to determine whether a person has Alzheimer’s, but MTBR-tau243 will be a very valuable complement in both clinical settings and research trials ,” says Hansson. “When both biomarkers are positive, the likelihood that Alzheimer’s is the underlying cause of a person’s cognitive symptoms increases significantly, compared to when only p-tau217 is abnormal. This distinction is crucial for selecting the most appropriate treatment for each patient.”
The Food and Drug Administration (FDA) has approved two Alzheimer’s therapies that slow the progression of the disease, although in Europe the European Medicines Agency has rejected their approval. Both work by reducing amyloid levels in the brain.
Horie explains that the number and variety of medications available for Alzheimer’s could soon increase, as several experimental drugs targeting the tau protein or other aspects of the disease are in development. With blood tests to diagnose and stage the disease, doctors could tailor treatments to each patient’s specific condition.
“ We are on the verge of entering the era of personalized medicine for Alzheimer’s disease ,” Horie says . “ In the early stages with low tau tangles, anti-amyloid therapies might be more effective than in the later stages. But after the onset of dementia with high tau tangles, anti-amyloid therapy or one of the many other experimental approaches might be more effective. Once we have a clinically available blood test for staging, along with effective treatments at different stages of the disease, physicians will be able to optimize their treatment plans based on each patient’s specific needs.”
Author: R. Ibarra
Source: abc.es and Nature
Date: 03/31/2025
Updated at 8:17 p.m.
Note: The Nutrigenomics Institute is not responsible for the opinions expressed in this article.
PHOTO FROM PIXABAY.
