New Alzheimer’s blood test offers hope for early detection

Scientists at Ruhr University Bochum in Germany have developed a new blood test for Alzheimer’s disease that is capable of detecting early indicators well before patients begin to exhibit symptoms. Although there is no cure for Alzheimer’s, researchers say early detection could open up new therapeutic opportunities.

Alzheimer’s disease is the most common type of dementia. Symptoms include memory loss, trouble concentrating, difficulty completing familiar tasks and confusion. Dementia affects around 50 million people worldwide, with nearly 10 million new cases every year, according to the World Health Organisation (WHO).

Alzheimer’s is characterised by the accumulation of amyloid-beta plaques, or sticky protein clusters, in the brain. These toxic substances begin to build up in the patient’s body 15-20 years before disease onset. According to a 2017 study by the University of Southern California, increased levels of amyloid plaque in the brain are the earliest signs of Alzheimer’s.

Published on Friday in the journal EMBO Molecular Medicine, the study evaluated whether the new blood test could accurately detect the presence of the pathological form of amyloid-beta in the blood in the early stages of the disease and before disease onset.

The new test works by measuring the amounts of healthy amyloid-beta and pathological amyloid-beta in the blood. Using data from a previous study, researchers tested blood samples of 65 participants who were later diagnosed with Alzheimer’s and more than 800 controls. The blood test detected signs of Alzheimer’s disease in asymptomatic individuals an average of eight years before diagnosis.

The test correctly identified individuals with Alzheimer’s 70% of the time and had an overall diagnostic accuracy of 86%. However, the test did produce some false positives – around 9% of test subjects that did not have Alzheimer’s were incorrectly detected as positive.

Currently, Alzheimer’s is diagnosed using costly positron emission tomography (PET) brain scans or by analysing samples of cerebrospinal fluid collected from patients through a lumbar puncture. The new blood test is a cheaper and simpler option that would allow doctors to screen the wider population and select individuals who could benefit from further testing. Doing so, researchers say, would help limit unnecessary invasive and costly testing procedures.

“At the moment, the test is not yet suitable for early diagnosis of Alzheimer’s because of the false positive results,” Klaus Gerwert, a professor at Ruhr University Bochum who led the research, told German magazine Focus. “But it opens the opportunity to filter out people in a cost-effective and minimally invasive screening.”

Gerwert, who developed the test, said it “shows a novel approach to detect early states of misfolding diseases, which could be extended to other diseases.”

The researchers intend to apply the blood test to detect Parkinson’s disease by substituting the amyloid-beta measure for alpha-synuclein, another disease biomarker, in a future study.