We’re entering an era of change in Alzheimer’s disease diagnosis, with the announcement of a new set of diagnostic guidelines for the disease. It’s hoped that a greater emphasis on blood biomarkers could help more patients be diagnosed earlier, and reduce the need for more invasive and expensive tests.
The new criteria have been developed by a team of experts with the backing of the International Alzheimer’s Association and the US National Institute on Aging.
Blood tests to detect Alzheimer’s disease have been in development for some years now, but it’s only recently that they’ve been convincingly shown to have potential in the clinic. Until now, only a few patients with access to specialized treatment centers have been able to obtain blood testing for Alzheimer’s, but scientists hope this could soon be much more widely available.
“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,” explained Charlotte Teunissen, a professor of neurochemistry at Amsterdam UMC who was involved in drafting the guidelines, in a statement.
For patients showing the first signs of cognitive impairment, which may or may not be related to Alzheimer’s disease, being able to confirm this with a simple blood test could provide peace of mind – or, in cases of early Alzheimer’s disease, it could allow people to start treatment before the disease has had a chance to cause severe damage to the brain.
Right now, Alzheimer’s diagnosis relies on finding evidence of the abnormal proteins that characterize the disease in samples of cerebrospinal fluid (CSF) or in the brain itself via a positron emission tomography (PET) scan.
CSF is obtained through a lumbar puncture, sometimes called a spinal tap, which is an invasive and sometimes uncomfortable procedure. Increased levels of the protein tau within the CSF indicate the presence of Alzheimer’s disease, although scientists are still divided on exactly why this increase occurs, even in patients without severe damage to the brain.
PET scans are non-invasive, but they are expensive and can be logistically complex to perform. An amyloid-PET scan detects the buildup of abnormal amyloid-beta protein in the brain, a hallmark of Alzheimer’s disease. A radioactive molecule that binds to the amyloid proteins is injected into the body, and the scanner picks up the small amount of radiation it emits.
The researchers presenting the new diagnostic guidelines highlighted that a blood test is relatively inexpensive, can be carried out in a range of settings, and should hopefully be a less stressful experience for patients. While lumbar punctures and PET scans may still be necessary in some cases, it’s hoped that the need for these will be reduced.
The announcement of the new guidance comes as lecanemab, a drug targeting the pathological amyloid plaques in Alzheimer’s patients, received full approval from the US Food and Drug Administration (FDA) in July 2023. The makers of a similar drug, donanemab, reported positive results from a Phase 3 clinical trial earlier this year. Research in other areas is moving forward apace, with big advances in vaccination technology targeting the disease.
Easier, earlier diagnosis, according to the teams behind the new guidelines, is the “gateway to treatment”, so the news could not be more timely. Research into blood biomarkers will continue and testing will be refined, but it’s another positive step forward in the fight against a disease that last year was estimated to be affecting 6.5 million older people in the US alone.
The new guidelines were presented at the Alzheimer's Association International Conference (AAIC) 2023.