Researchers at the University of Washington School of Medicine in St. Louis suggest that they can measure levels of Alzheimer's beta amyloid protein in the blood and use these levels to predict whether protein has accumulated in the brain.
This protein is important, because it begins to accumulate up to twenty years before people develop Alzheimer's. Now measuring these levels is very easy thanks to a blood test.
When blood amyloid levels are combined with two other major Alzheimer's risk factors (age and the presence of the APOE4 genetic variant), people with early Alzheimer's brain changes can be identified with an accuracy of 94%, according to the study published by these researchers in the journal Neurology.
Surprisingly, the test may be even more sensitive than a PET brain scanner to detect the onset of amyloid deposition in the brain. This milestone represents another step towards a blood test to identify people on the way to developing Alzheimer's before symptoms appear.
The test uses a technique called mass spectrometry to accurately measure the amounts of two forms of beta amyloid in the blood: beta 42 amyloid and beta 40 amyloid. The ratio of the two forms decreases as the amount of beta amyloid deposits in the brain increases.
In the current study, 158 adults over 50 years old participated. All but 10 of the participants in the new study were cognitively normal, and each provided at least one blood sample and underwent a PET brain scan. The researchers classified each blood sample and PET scan as positive or negative amyloid, and found that each participant's blood test agreed with their PET scan 88 percent of the time, which is promising but not accurate enough. for a clinical diagnostic test.
In an effort to improve the accuracy of the test, the researchers incorporated several important risk factors for Alzheimer's. Age is the largest known risk factor; After age 65, the probability of developing the disease doubles every five years. A genetic variant called APOE4 increases the risk of developing Alzheimer's three to five times. And gender also plays a role: two out of every three Alzheimer's patients are women. When the researchers included these risk factors in the analysis, they found that age and APOE4 status raised the accuracy of the blood test to 94%.. Sex did not significantly affect the analysis.
This analysis may be available in medical offices within a few years, but its benefits will be much greater once there are treatments to stop the disease process and prevent dementia. That means we can enroll subjects more efficiently in clinical trials, which will help us find treatments faster and could have a huge impact on the cost of the disease, as well as the human suffering that accompanies it.