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TORONTO — A new test developed by neuroscientists at the University of Pittsburgh can detect signs of Alzheimer's disease in a blood sample more accurately than previous tests, by spotting an elusive sign of the disease.
The test works by detecting a novel biomarker of Alzheimer's called brain-derived tau, according to a study by the team published in the medical journal Brain on Monday.
Tau is a protein that supports neurons, or nerve cells, in the brain. The abnormal accumulation of tau, especially in tangles of the protein, is a hallmark of Alzheimer's disease. While tau is associated mostly with brain cells, cells outside the body can produce a variation the study calls "big tau."
By figuring out how to detect brain-derived tau in blood, the team has created a method for diagnosing Alzheimer's that is more accessible than existing methods.
"At present, diagnosing Alzheimer's disease requires neuroimaging," senior author Thomas Karikari said in a media release issued on Monday. "Those tests are expensive and take a long time to schedule, and a lot of patients, even in the U.S., don't have access to MRI and PET scanners."
The current framework for detecting Alzheimer's, set by the U.S. National Institute on Aging and the Alzheimer's Association, is called the amyloid, tau and neurodegeneration method.
This method requires scientists to detect three components, or biomarkers, of Alzheimer's disease – amyloid plaques, tau tangles and neurodegeneration — in the brain. It can be achieved either through imaging or by analyzing cerebrospinal fluid samples, but Karikari said these methods are costly and require a lot of resources. So Karikari's team set out to develop a simple, minimally-invasive and cost-effective blood test that could detect the same biomarkers.
"The most important utility of blood biomarkers is to make people's lives better and to improve clinical confidence and risk prediction in Alzheimer's disease diagnosis," Karikari said.
The most important utility of blood biomarkers is to make people's lives better and to improve clinical confidence and risk prediction in Alzheimer's disease diagnosis.
–Thomas Karikari, senior study author
Up until now, blood diagnostic methods have been able to detect two out of three of the biomarkers needed to diagnose Alzheimer's – amyloid and a version of tau. However, they've struggled to detect the third component – neurodegeneration markers specific to Alzheimer's. So the team developed a technique to distinguish brain-derived tau in blood from free-floating big tau using a special antibody that selectively binds to brain-derived tau.
Karikari and his team hope this new, more accessible blood diagnostic technique can improve clinical trial design and expand trial enrolment to include patients from populations that have historically been overlooked by such trials. To that end, they are planning to conduct large-scale clinical blood screening for brain-derived tau in a wide range of participants from diverse racial and ethnic backgrounds, memory clinics and the community.
"There is a huge need for diversity in clinical research, not just by skin color but also by socioeconomic background," Karikari said.
"To develop better drugs, trials need to enroll people from varied backgrounds and not just those who live close to academic medical centers. A blood test is cheaper, safer and easier to administer, and it can improve clinical confidence in diagnosing Alzheimer's and selecting participants for clinical trial and disease monitoring."
