The presence of a specific form of tau protein in blood could help in early detection of amyloid plaque formation in the brain leading to Alzheimer’s disease, according to recent research published in the Journal of Experimental Medicine.
Alzheimer’s disease begins with a silent phase lasting two decades or more during which amyloid plaques slowly collect in the brain without causing obvious cognitive problems.
The researchers at the Washington University in St. Louis utilised mass spectrometry to identify and measure the different forms of tau in the blood samples. They found that levels of a form of tau known as phosphorylated-tau-217 correlated with the presence of amyloid plaques in the brain. People with amyloid in their brains had two to three times more of the protein in their blood than people without amyloid revealed the study. The high levels were evident even in people even before signs of cognitive decline.
This will help to identify and predict people who have or will likely develop Alzheimer’s disease, says senior author Randall J. Bateman, Professor of Neurology at Washington University in St. Louis.
The researchers analyzed blood samples and brain scans from 34 people who participated in the Alzheimer’s research studies at the University’s Charles F and Joanne Knight Alzheimer’s Disease Research Center. 19 of the participants had no amyloid in their brains, 5 had amyloid but no cognitive symptoms and 10 had amyloid and cognitive symptoms.
To verify their findings, the researchers repeated the analysis in a separate group of 92 people: 42 with no amyloid, 20 with amyloid but no cognitive symptoms, and 30 with amyloid and symptoms. In this analysis, levels of phosphorylated-tau-217 in the blood correlated with the presence of amyloid in the brain with more than 90% accuracy, noted the authors.
When the team looked only at people with no cognitive symptoms, blood levels of phosphorylated-tau-217 distinguished those in the early, asymptomatic stage of Alzheimer’s disease from healthy people with 86% accuracy.
“This is just an exploratory study, but we think phosphorylated tau 217 is a promising target for an early diagnostic test,” said Nicolas Barthélemy, Department of Neurology, Washington University School of Medicine, St. Louis.
“There was a large difference between the amyloid-positive and amyloid-negative groups, even amongst people who were cognitively normal. We did have to use a large volume of blood in this study, but we’re working on reducing the volume.”
The team is researching on improving the procedure to prepare and concentrate the samples in order to develop a tau-based blood test that can identify people at risk of developing Alzheimer’s dementia before symptoms arise.