We confirm the use of the p-tau217 blood biomarker to detect Alzheimer's disease in its early stages

Detecting Alzheimer's disease in its earliest stages is critical to applying preventive strategies and optimizing new treatments acting on the proteins which cause the disease. An international study, led by Lund University (Sweden), with the participation of the Barcelonaβeta Brain Research Center (BBRC), a research site of the Pasqual Maragall Foundation, has shown that a blood test based on the p-tau217 biomarker can effectively identify individuals without cognitive impairment, but with beta amyloid accumulation, one of the main brain alterations typical of Alzheimer's disease. 

The publication led by Dr Gemma Salvadó, head of the BBRC neuroimaging group, with the participation of Hospital de Sant Pau, included 12 independent cohorts from Europe, the USA, Canada and Australia. The research, published in the JAMA Neurology journal, used samples from 2,916 participants without symptoms of cognitive impairment, among them 395 cognitively healthy adults from the ALFA+ cohort, which is part of BBRC's ALFA study, promoted by the “La Caixa” Foundation.

The results of this study add to the current evidence and reinforce the potential of blood biomarkers as a tool for early detection of the disease. Specifically, the study shows that the detection of p-tau217 in plasma offers an accuracy of 81% to correctly identify beta amyloid positivity, which suggests that it is a good screening method for selecting participants for clinical trials. Furthermore, when combined with a second confirmatory test (a PET scan or cerebrospinal fluid analysis), accuracy increases to 91%.

This two-step approach is highly effective in reducing false positives while substantially reducing costs and the burden on patients by avoiding the need to routinely perform invasive or expensive tests on everyone, reserving them only for cases where the blood test suggests a high risk of the disease. 

“These results reinforce the usefulness of the blood test for p-tau217 as a starting screening tool in individuals without symptoms, especially at a time when clinical trials and disease-changing treatments require the identification of very early cases,” explains Dr Gemma Salvadó, main author of the study and principal investigator at the Barcelonaβeta Brain Research Center Neuroimaging Group.

A key biomarker for early intervention and screening of participants in clinical trials

Alzheimer's disease currently affects more than 55 million people worldwide. Targeted therapies against the beta amyloid protein have shown modest benefits in symptomatic phases. Therefore, the focus of research is now on early detection and intervention in preclinical phases, when the pathology is present but symptoms have not yet appeared.

Blood biomarkers represent a more accessible and scalable alternative to invasive tests such as lumbar puncture or expensive tests such as positron emission tomography (PET). Among them, the p-tau217 protein has been established as the most accurate marker for detecting Alzheimer's disease.

In this study, a two-step diagnostic workflow was assessed: first, an initial screening with the plasma biomarker p-tau217, and then, when necessary, confirmation with PET or cerebrospinal fluid analysis. This approach allowed a reduction of more than 40% in these invasive and expensive tests, compared to a procedure that does not require blood screening, without compromising reliability of the diagnosis.

The study authors note that further research is still needed to establish reliable and generalizable cut-off points for the blood biomarker, and to validate the results in more diverse populations. Nevertheless, the findings highlight the clinical usefulness of plasma p-tau217 as a screening tool for early detection of Alzheimer's disease, for the screening of participants in clinical trials, and, in the future, to guide access to disease-modifying treatments. Furthermore, when combined with cognitive assessment, this blood test is emerging as an effective screening strategy in both primary and specialized care.

Reference article: Salvadó G, Janelidze S, Bali D, Orduña A, Therriault J, Brum W, Pichet A, Stomrud W, Nattsson-Carlgren N, Palmqvist S, Coomans E, Teunissen C, van der Flier W, Rahmouni N, Benzinger T, Domingo J, Blennow K, Doré V, Feizpour A, Rowe C, Alcolea D, Fortea J, Villeneuve S, Johnson S, Rosa-Nieto P, Petersen R, Clifford J, Shindler S, Suárez-Calvet M, Ossenkoppele R, Hansson O, ADNI, ALFA and PREVENT-AD Study Groups. Plasma Phosphorylated Tau 217 to Identify Preclinical Alzheimer Disease. JAMA Neurol. September 15, 2025. doi: 10.1001/jamaneurol.2025.3217