Simple blood test could help early Alzheimer’s diagnosis and direct treatment

31st January 2024

A simple blood test to diagnose Alzheimer’s disease could be as accurate as a lumbar puncture or expensive brain scans, according to a new study.

It raises the potential for early diagnosis to make best use of new medicines that slow the rate of cognitive decline but also could help doctors distinguish between different types of dementia in order to direct treatment.

The test, which is commercially available, measures levels of p-tau217 in plasma samples – a biomarker that can be used to detect a build-up of amyloid and tau proteins in the brain.

Research done in three separate groups of patients over eight years found the precision of the blood test was comparable to cerebrospinal fluid biomarkers.

It was particularly effective in detecting longitudinal changes, even in preclinical stages of the disease, the researchers reported in the journal JAMA Neurology.

The test could also significantly reduce the need for additional confirmatory tests patients have to have to verify their diagnosis, the international team of researchers said.

Study author Dr Daniel Alcolea, researcher at the Dementia Neurobiology Group at the Sant Pau Research Institute in Barcelona and head of the biomarkers platform at Hospital Sant Pau’s Memory Unit, said: ‘This biomarker has shown very high performance in detecting Alzheimer’s in blood, with an accuracy between 90 and 95%.

‘Of all the biomarkers currently being studied for diagnosing Alzheimer’s disease, this one has shown the best results.’

Dr Richard Oakley, associate director of research and innovation at Alzheimer’s Society, said there were potentially ground-breaking new drugs which can slow the progression of early-stage Alzheimer’s disease in the development pipeline.

‘But for people to be eligible for them if they’re approved in the UK, they will need an early, accurate diagnosis. This study is a hugely welcome step in the right direction,’ he said.

Professor David Curtis, honorary professor at the UCL Genetics Institute, said the test potentially had huge implications for screening, diagnosis and developing better treatments.

‘When effective treatments to prevent the progression of Alzheimer’s disease become available it will be essential to be able to identify people who are at high risk before they begin to deteriorate.

‘This study shows that a simple blood test might be able to do this by measuring levels of tau protein in the blood which has been phosphorylated in a specific way.’

The only way to prove someone has a build-up of Alzheimer’s-related proteins in the brain currently is through a lumbar puncture or an amyloid PET scan, which are only available in around one in 20 memory clinics, said Professor Charles Marshall, professor of clinical neurology at Queen Mary University of London.

‘Before these tests become widely used in the NHS, we will need further evidence to show that the blood test can accurately diagnose who is in the process of developing dementia, and that it can identify who is likely to benefit from treatments to slow down the disease’, he said.

‘We will also need to ensure that the blood test performs equally well in more diverse populations, so that it does not worsen existing health inequalities in access to diagnosis and treatment for dementia.’ 

A version of this article was originally published by our sister publication Pulse.

New approach to Alzheimer’s diagnosis unveiled as consultation opens for feedback

17th July 2023

Diagnosing Alzheimer’s disease through the use of blood biomarkers could transform care for patients after new proposed guidelines were presented at the International Alzheimer’s Congress in Amsterdam.

Developed by clinicians and researchers from around the world, the proposed guidelines incorporate blood-based biomarkers, which offer a low cost and easily accessible alternative to more traditional routes of diagnosis.

A blood test has been developed for this purpose in recent years, which has shown good results, and this can be used outside of specialist clinics, meaning underserved and rural populations can also benefit.

Charlotte Teunissen, professor of neurochemistry at Amsterdam University Medical Centre, who was involved in drafting the new guidelines, said: ‘A new generation of biomarkers is now available to detect Alzheimer’s disease more and more effectively. We have already gained a lot of experience with this in our Alzheimer’s centre, but in the long term the test can also be successfully implemented after a GP’s referral.‘

Diagnosing Alzheimer’s earlier

Currently, Alzheimer’s is diagnosed through the analysis of cerebrospinal fluid, acquired through an invasive lumbar puncture, or via an expensive PET scan. The proposed diagnostic criteria would prove less stressful to patients as well as speeding up diagnosis, offering a gateway to earlier treatment and allowing patients to make more informed decisions about their treatment and disease management.

Defining neurodegenerative diseases biologically, rather than based on syndromic presentation, has become a unifying concept common to all neurodegenerative diseases, not just Alzheimer’s.

While many biomarkers have shown promise and performance in the ability to detect Alzheimer’s disease, some of the biomarkers described in the proposal have not yet been extensively tested in broadly representative populations, and further analysis in these groups is urgently needed, the Alzheimer’s Association said.

The draft proposal will be open for consultation for 30 days, and the working group invites comments from scientific and clinical audiences.

Maria C. Carrillo, chief science officer, Alzheimer’s Association, said: ‘Care has to evolve with the science. Our understanding of Alzheimer’s disease has advanced, in particular our understanding of biomarkers, and this needs to be reflected in how we describe and diagnose the disease.

‘We look forward to input from the scientific and clinical community on these proposed revisions. The Alzheimer’s Association is proud to lead this important effort, which will ultimately enable people to get a more accurate diagnosis earlier, as well as help those diagnosed enrol in research trials and, if appropriate, get access to approved treatments.‘