Illustration of human blood cells
(Photo: Getty Images)
A blood test developed to detect Alzheimer’s disease can also show how far the disease has progressed and tell if symptoms are due to Alzheimer’s or another cause, a study finds. The report from researchers at Washington University School of Medicine in St. Louis and Lund University in Sweden was published Monday in Nature Medicine.
Levels of the MTBR-tau243 in the blood show the accumulation of tau aggregates in the brain, which correlates with Alzheimer’s disease severity. Specifically, the team evaluated MTBR-tau243 levels in people with cognitive decline so they could tell if the person had early- or late-stage Alzheimer’s disease. It also could discern if the people had symptoms that weren’t from Alzheimer’s disease.
“This blood test clearly identifies Alzheimer’s tau tangles, which is our best biomarker measure of Alzheimer’s symptoms and dementia,” Randall J. Bateman, MD, a senior author and professor of neurology at WashU Medicine, said in a statement.
The team used brain scans to gauge tau tangles and measured MTBR-tau243 from blood samples. Data came from two groups: 108 people at WashU Medicine’s Charles F. and Joanne Knight Alzheimer Disease Research Center, and 55 participants from the Swedish BioFINDER-2 cohort. Researchers also used another dataset of 739 people in the BioFINDER-2 cohort to generalize the results.
The analysis showed that blood MTBR-tau243 levels reflected the amount of tau tangles with 92% accuracy. MTBR-tau243 levels in the blood were normal in people who didn’t have symptoms regardless of their amyloid status, which indicates that MTBR-tau243 levels didn’t shift in healthy people nor in those with Alzheimer’s disease who had amyloid plaques but no symptoms.
People with Alzheimer’s disease symptoms and mild cognitive impairment had elevated levels of MTBR-tau243; levels were much higher — up to 200 times — for those with dementia.
MTBR-tau243 levels were normal in people with cognitive symptoms due to diseases other than Alzheimer’s, meaning that the test worked to discern Alzheimer’s dementia from other kinds of dementia.
People with Alzheimer’s have a buildup of the amyloid protein, which forms plaques in the brain. Years later, tangles of tau protein emerge, which is around when symptoms start. Positron emission tomography (PET) brain scans, though accurate, are expensive, time-consuming and difficult to access if the patient isn’t near a major research center. This is why there is interest in the research community on other tests.
Bateman has already created two currently used blood tests that show how much amyloid plaques are in the brain.