Researchers have developed a blood test that correlates well with levels of amyloid-β in the brain, offering an opportunity to reduce the cost of assessing potential therapies to treat Alzheimer's disease. Currently the only reliable methods are invasive or expensive, requiring access to cerebrospinal fluid or the use of scanning technologies. This work might be considered in the broader context of a range of studies linking amyloid-β in blood vessels and bloodstream with amyloid-β in the brain; it is thought that the relationship between amyloid-β inside and outside the brain may be a two-way street, a form of equilibrium. On the one hand that means that it might be possible to leach amyloid-β from the brain by clearing it from the cardiovascular system. On the other hand, it may be the case that increased amyloid-β in the cardiovascular system due to aging is an early source of the amyloid protein aggregates that emerge in the brain.
Researchers have developed the first blood test to detect amyloid-β protein buildup in the brain, one of the earliest hallmarks of Alzheimer's disease. The findings show that measurements of the protein and its precursors in the blood can predict neural amyloid-β deposition and could pave the way for a cheap and minimally invasive screening tool for the disease. "This study has major implications. It is the first time a group has shown a strong association of blood plasma amyloid with brain and cerebrospinal fluid."
Current methods to identify amyloid-β buildup in living people are limited to costly and sometimes highly invasive procedures, such as brain imaging with a PET scanner and spinal cord fluid extraction. So researchers set out to test whether the same information could be obtained from a blood sample. Using immunoprecipitation and mass spectrometry, the team isolated and characterized amyloid proteins in the blood from a cohort of 121 people in Japan spanning a range of cognitive function, from normal to developed Alzheimer's. They showed that blood test results could predict amyloid-β levels in the brain with about 90 percent of the accuracy achieved using PET scanning. A repeat of the approach with a validation cohort of 252 people in Australia confirmed the blood test's performance.
Such a test could one day be used to detect early signs of Alzheimer's in people with no obvious symptoms. "I can see in the future, five years from now, where people have a regular checkup every five years after age 55 or 60 to determine whether they are on the Alzheimer's pathway or not. If a person knows they are on this pathway well before the onset of any cognitive impairment some would want to alter their lifestyles. It's good to see this type of study advance, as we desperately need noninvasive and low-cost markers for Alzheimer's disease. But still, at this point it is not ready for prime time."