New blood test could detect Alzheimer's long before symptoms

A low-cost blood test could diagnose Alzheimer’s disease up to 20 years before the onset of symptoms, according to new research by Macquarie University.

The research claims to be the first to show higher blood levels of Alzheimer’s-related proteins in cognitively normal older adults whose brain scans showed pre-clinical Alzheimer’s, than in otherwise similar adults with normal brain tissue.

More than 300,000 Australians suffer from this degenerative brain disease. The current diagnosis of the disease relies on cognitive tests which are not sensitive enough to detect changes in the brain before a person already shows symptoms.

The brain changes from Alzheimer’s disease include abnormal protein build-up, which damages connections between brain cells and causes eventual cell death, shrinking brain volume. While the changes occur gradually, it can be more than 15 years before the accumulated damage is noticeable through behavioural change.

Scientists currently use specialised tests to identify these abnormal brain tissue changes in living patients, however these tests are expensive and/or invasive, making them unsuitable for widespread screening.

The research, headed by neurobiologist Professor Ralph Martins from Macquarie University’s Department of Biomedical Sciences, who is also Foundation Chair of Ageing and Alzheimer’s Disease at Edith Cowan University in Western Australia, involved an international, multi-disciplinary team from around Australia, the UK, the USA, Sweden and Belgium.

The Macquarie University-led study included 100 volunteers aged from 65 to 90 from the Kerr Anglican Retirement Village (co-established and coordinated by study co-author Associate Professor Kathryn Goozee), who were screened to exclude those with signs of cognitive impairment or other significant health factors.

All of the volunteers also had their brains scanned using a PET amyloid analysis, and researchers identified those with pre-clinical Alzheimer’s based on the presence of abnormal protein deposits, or brain amyloidosis. 

The blood proteins of all the volunteers were compared, and the results showed that people with pre-clinical Alzheimer’s also showed higher blood levels of three proteins: GFAP, p-tau181 and p-tau231.

Other risk factors for Alzheimer’s disease, including age, sex and a higher genetic predisposition were assessed through the presence of the Apolipoprotein E allele.

Researchers found that using GFAP in a statistical model with these risk factors gave a high accuracy of 86%, in distinguishing between people with pre-clinical Alzheimer’s disease and cognitively normal older people without Alzheimer’s-specific abnormal brain tissue changes.

“We also found for the first time, that levels of GFAP and p-tau181 levels increased in pre-clinical Alzheimer’s patients over 12 months, but these didn’t increase in cognitively normal older people without Alzheimer’s-specific abnormal brain tissue changes,” Professor Ralph Martins said.

“Our findings highlight promising biomarkers for use in early diagnostic and prognostic blood tests for Alzheimer’s disease, prior to symptoms,” said Macquarie University’s Department of Biomedical Sciences Research Fellow and lead author, Dr Pratishtha Chatterjee. The study was published in the journal Alzheimer’s & Dementia.

These findings will allow more cost-effective screening and prognosis in clinical trials, Chatterjee said.

A PET brain amyloid scan can cost upwards of $2000 in Australia, and up to five times more in the US, so running clinical trials with hundreds or thousands of people would be prohibitively expensive — whereas blood tests would likely be under $50 each, at scale, Martins said.

“Being able to more easily identify people with very early signs of Alzheimer’s disease is a real game-changer, it will allow clinical trials that are much more robust and potentially identify earlier interventions,” Martins said.

Image credit: ©stock.adobe.com/au/Kateryna_Kon