By Holly Giles
Alzheimer’s, the most common type of dementia, is associated with a loss of brain function that impacts the daily lives of over 850,000 people in the UK. This figure is rising every year as people are living longer.
Alzheimer’s is currently diagnosed by observing behaviour and memory changes, and then officially diagnosed after death. However, last week a new study was published that promises a blood test which could not only accurately diagnose dementia but could show the start of the disease up to twenty years before symptoms are seen.
In a patient with Alzheimer’s there is a deposition of amyloid plaques and tau tangles in the brain. The plaques are found between neurons and disrupt their communication. The tau tangles are collections of tau proteins within neurons. Tau is a naturally occurring protein that attaches to the scaffolding structures within neurons. In Alzheimer’s the proteins detach from the scaffolding and are able to stick together, to form tangles inside neurons. This prevents the neuron from signalling efficiently and disrupts brain communication. It is this altered communication within the brain that is responsible for the effects seen in Alzheimer’s patients.
The international study, published last week, found that a blood test able to monitor the level of a specific tau protein, phosphotau216, could indicate the presence of tangles and plaques, and from this could suggest Alzheimer’s.
The research was conducted in 1402 impaired and unimpaired participants in Arizona, Sweden and Columbia. The international study showed promising results with the blood test about to discriminate between “intermediate or high likelihood of Alzheimer’s” and unimpaired patients with an accuracy of 89% in Arizona and 96% in Sweden.
In Columbia, the test was used to distinguish between people who carried a genetic mutation predisposing them to the condition and those who didn’t. This allowed distinction twenty years before they are expected to develop the condition, allowing time for preventative measures to be trialled.
The significance of these results cannot be underestimated, explained Eric Reiman, executive Director of Banner Alzheimer’s Institute in Phoenix, and senior author of the study:
“Blood tests like p-tau217 have the potential to revolutionise Alzheimer’s research, treatment and prevention trials, and clinical care … While there’s more work to do, I anticipate that their impact in both the research and clinical setting will become readily apparent within the next two years”
The Director of the National Institute of Ageing, Dr Richard J. Hodes added:
“The considerable time and resources required for screening research participants with PET scans and spinal taps slow the pace of enrollment for Alzheimer’s disease treatment studies … The development of a blood test would enable us to rapidly screen a much larger and more diverse group of volunteers who wish to enroll in studies.”
It may be some time before we see this blood test being used as common practice in Alzheimer’s care but it proves a principle that one day we will be able to test for the condition both when it is present and when it is developing. This could revolutionise the way we treat the condition and change the experience for patients everywhere.