13 August 2019

The best-established neuroimaging biomarker of AD is considered to be hippocampus volume loss, which discriminates AD from healthy controls with high accuracy (Apostolova et al., 2007). However new data from researchers have suggested blood tests are highly accurate at identifying Alzheimer’s before symptoms arise. Are diagnosis paradigms changing? Can new blood tests offer a potential method to screen large numbers of patients efficiently for entry into clinical trials, thus accelerating the search for a cure for AD?

Researchers from Washington University School of Medicine in St. Louis have reported that by using mass spectrometry they can precisely measure levels of the Alzheimer's protein amyloid beta in the blood to predict whether the protein has accumulated in the brain. The study found that when blood amyloid levels are combined with two other major Alzheimer’s risk factors, age and the presence of the genetic variant APOE4, people with early Alzheimer’s brain changes can be identified with 94% accuracy.

The blood test could provide a way to efficiently screen for people with early signs of disease so that they can participate in clinical trials evaluating whether drugs can prevent Alzheimer’s dementia. The current methodology involves screening for clinical trials with PET brain scans, which are not only very expensive but also time-consuming.

Of particular interest was the apparent discordance between some people’s blood tests and brain scans, with the blood test being positive for amyloid beta but the brain scan negative. However, on follow-up, on average four years later, those with mismatched results tested positive on subsequent brain scans, suggesting that the blood test was a better predictor of early signs of the disease than the gold standard brain scan.

This encouraging report of a predictive blood amyloid test follows several reports of AD blood test research presented by other groups at the Alzheimer’s Association International Conference in Los Angeles last month. Although there is still no cure for AD, a test that allows diagnosis before symptoms arise could be very helpful for clinical trial screening, allowing inclusion of patients at an early stage of the disease, when treatments might be more effective.