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Blood samples in vials © Photo by Karolina Grabowska from Pexels

The study, part-funded by DPUK, was carried out with a group of 400 volunteers from the Medical Research Council National Survey of Health and Development (NSHD) 1946 British Birth Cohort. The participants had amyloid PET scans and blood tests as part of the Alzheimer’s Research UK-funded Insight 46 study.

The findings, published in the journal Brain, suggest blood tests could be used to recruit people to Alzheimer's drug trials before they start showing symptoms.

The researchers tested three different ways of measuring proteins in the blood and compared the results of the blood tests to those from the PET scans. The best-performing blood test was able to identify individuals with high levels of amyloid with about 85% accuracy. Using blood tests to screen for amyloid would reduce the requirement for PET scans by roughly half.

Amyloid is a protein that builds up in the brain in Alzheimer's and is thought to trigger processes that result in damage to the brain and the symptoms of the disease. Amyloid accumulates in the brain years before symptoms appear, but most amyloid-lowering drug trials so far have involved people who already have symptoms­ – an approach that has yet to result in a new treatment.

Lead author Professor Jonathan Schott, of the Dementia Research Centre at UCL, said: 'Current evidence suggests that the brain changes leading to Alzheimer's disease start many years before symptoms. Identifying individuals at risk opens a window of opportunity to offer treatments to prevent the onset of cognitive decline.

'Our results – from a sample of individuals from across mainland Britain who were all born in the same week in 1946 – show that blood tests may be a useful means of identifying individuals who are in the earliest stages of the disease.

'In the short term, this has implications for clinical trials of new treatments for Alzheimer's disease. Blood tests could allow for rapid screening, and reduction of the numbers who would need more expensive PET scans before entering a study. This would considerably reduce the costs and time it takes to run clinical trials, and will hopefully accelerate the development of new treatments.'

Dr Ashvini Keshavan of UCL, first author on the study, added: 'In due course blood tests have the potential to revolutionise how we diagnose Alzheimer's disease, allowing access to better diagnostic tests in the community, and particularly in settings where more expensive PET scans and lumbar puncture tests are not currently available, thus making access to any new treatments and support more equitable.'

Read the full story on the Alzheimer's Research UK website or on the UCL website.