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.’