A new blood test being trialed in Brazil appears able to detect Alzheimer’s disease with accuracy above 90%, according to a multinational study led in part by researchers at the Federal University of Rio Grande do Sul (UFRGS). The results were published in the journal Molecular Psychiatry on September 8.
Researchers set out to identify the most reliable blood biomarker (or combination of biomarkers) for Alzheimer’s. After reviewing results from more than 110 prior studies involving roughly 30,000 people, the team focused on four candidate markers: amyloid-β peptides Aβ40 and Aβ42, phosphorylated tau at position 217 (p-tau217), neurofilament light chain (NfL) and glial fibrillary acidic protein (GFAP). They then measured these markers in blood samples from 59 individuals — 20 cognitively healthy people, 22 diagnosed with Alzheimer’s, and 17 with vascular dementia — and compared the blood results with cerebrospinal fluid (CSF) findings, the diagnostic “gold standard.”
Of the four markers tested, plasma p-tau217 performed best. In this cohort it matched the CSF diagnosis with accuracy above the 90% level cited by the World Health Organization as a benchmark for a gold-standard test, making p-tau217 the most promising single blood marker identified by the study.
“The practical challenge is access,[…]Both the cerebrospinal fluid test and tomography can be ordered by the doctor for biomarker-assisted diagnosis of Alzheimer’s disease. The problem is that when we think of a country like Brazil, continental, with 160 million people who depend on the SUS, how are we going to carry out these exams on a large scale? A lumbar puncture requires infrastructure, experience and is normally performed by a neurologist. And the imaging exam is very expensive to use in the SUS across the country.”
– Eduardo Zimmer, a UFRGS professor who supervised the research, in an interview with Agência Brasil.
Blood-based Alzheimer tests already exist in private markets abroad — for example, tests that measure combinations of the biomarkers used in this study — but they are costly when offered in Brazil; one such test has been reported at prices up to about R$3,600 in private settings. The Brazilian team argues that a validated national test could expand equitable access if incorporated into the public health system (SUS).
Next steps and public-health aims
The project is part of the IB-BioNeuro initiative (Brazilian Initiative for Biomarkers in Neurodegenerative Diseases), which includes UFRGS, the Federal University of Pelotas (UFPel), the Rio Grande do Sul health secretariat and other partners, with support from the Serrapilheira Institute and equipment collaboration with the US firm Quanterix. The researchers plan a much larger validation phase: roughly 3,000 participants across 10 cities in Rio Grande do Sul to test accuracy at scale and investigate whether the blood marker can identify Alzheimer’s before symptoms appear. That phase is expected to run for about two years; if successful, the team says it will pursue ways to make the test available within public health services by 2028. (Agência Brasil)
“We will start the studies with individuals over 55 years old, because we know there is a phase we call the preclinical phase of Alzheimer’s disease, which is when the disease begins to take hold but the individual still has no symptoms. The idea is also to map the prevalence of these individuals. We need several evaluations to understand where the analyses will be done, when these tests will be used, which population will benefit, and whether it will speed up diagnosis in the SUS.”
– Eduardo Zimmer
Why this matters
Early and accurate diagnosis is a major global challenge. The World Health Organization estimates that about 57 million people were living with dementia worldwide (with Alzheimer’s comprising the majority of cases), and the number of people with dementia is expected to grow as populations age. In Brazil, national reports estimate roughly 1.8 million people currently live with dementia, a figure projected to rise markedly by mid-century — underlining the urgency of scalable, affordable diagnostic tools.
Caveats
The Brazilian results are encouraging but preliminary. The study’s sample used for direct blood-to-CSF comparisons was small (59 people), and experts caution that larger, diverse population studies are required to confirm diagnostic performance, rule out biases and understand how tests perform across different ethnic and educational backgrounds. The researchers themselves emphasize that more evaluations are needed to define when and where blood testing should be used, and which groups will benefit most.
If larger trials confirm the findings, a reliable blood test based on p-tau217 could transform the pathway to diagnosis in Brazil and other middle-income countries — lowering costs, reducing dependence on specialist procedures and enabling earlier identification of people who may benefit from monitoring or future therapies. For now, scientists say the new data are a hopeful step toward that goal.
Source: UOL
