A new blood test could help with the early detection of Alzheimer's, according to a study

The researchers have looked at what happens when testing 1350 people, with an average age of 61, with the new blood tests that pick up the underlying protein changes that occur in Alzheimer’s disease. A relatively small proportion of people without dementia (15% or less, depending on the particular test) tested positive on these blood tests and these individuals tended to do worse on some, but not all, tests of thinking. 

This study has used the new blood tests-that have started to enter clinical practice-in a relatively large number of people below the age where cognitive symptoms become most frequent. This adds to our knowledge about how many people will have abnormal Alzheimer’s blood results at this age, and provides further information about how common these changes are. Because it is at a single time point, it does not tell us how about how the proportions in this group will change over time. It also only tested people who had managed to continue to be part of a study for several decades, and we do not know how this will have affected the proportions.

It is essential that we continue doing research like this and into the processes that lead to altered brain function in Alzheimer’s and other dementias. It is also critical that we keep in mind that having an abnormal blood test is not in itself a clinical diagnosis and does not mean that someone will inevitably get dementia. At the moment we only really understand what these tests mean when there is evidence of cognitive impairment, so they can be helpful where there has been a clinical assessment but we do not yet fully understand their implications when they have been done without any such assessment or in people where there is no objective evidence of cognitive difficulties.

Dementia is the UK’s biggest killer and early and accurate diagnoses have never been more important. Blood-based biomarkers offer a promising, cost-effective and less invasive way of detecting Alzheimer's disease so it’s encouraging to see momentum in this area.

Earlier diagnosis unlocks access to treatments, support and help sooner. This study suggests blood tests could help detect Alzheimer’s disease in people in their early 60s – a group largely overlooked in previous research, which focused on older adults.  While we’re not yet at the point of screening people before symptoms appear, work like this suggests this may be a reality in the future.

By looking at these biomarkers in a more diverse population, the study made an important step in understanding the potential use of these blood tests for everyone. However, more research is still needed to explore how results may differ depending on a person’s race, sex and genetics.

Innovative approaches like this and the Blood Biomarker Challenge – led by Alzheimer’s Society, Alzheimer’s Research UK with Postcode Lottery funding – are critical to bringing blood tests for dementia to the NHS in the next five years.