Researchers are making headway in developing a blood test for the presence of tau, one of the hallmarks of Alzheimer’s Disease (AD).
In one new development, experts at the University of California, San Francisco (UCSF) compared phosphorylated-tau181 (P-tau181) to a related form of tau called P-tau217 to determine which can best identify individuals with AD.
Results showed that the two biomarkers were similar overall, but P-tau 217 had a slight edge in terms of accuracy. Importantly, both tau isoforms distinguished frontotemporal lobar degeneration (FTLD).
“These new blood tests for P-tau are going to be really exciting because they will improve our ability to simply and inexpensively assess whether someone is at high risk for having Alzheimer’s Disease,” study author Adam L. Boxer, MD, PhD, professor in UCSF’s Department of Neurology, told Medscape Medical News.
Dr Adam Boxer
With the approval of the first disease-modifying therapy for AD possibly around the corner, developing an accurate diagnostic blood test for this condition is even more urgent, added Boxer, who is also director of UCSF’s Neurosciences Clinical Research Unit and AD and FTD Clinical Trials Program.
The findings were presented at the Alzheimer’s Association International Conference (AAIC) 2020, which was held online this year because of the COVID-19 pandemic.
Important Implications
Currently, the only approved AD biomarkers are expensive positron emission tomography (PET) scans using agents that detect tau or amyloid, another hallmark AD protein, and cerebrospinal fluid levels of amyloid and tau, the measurement of which entails invasive lumbar puncture procedures.
This limits the ability to easily confirm the underlying cause of dementia or cognitive impairment, which “obviously has important prognostic and therapeutic implications,” said Boxer.
Having a plasma biomarker, especially for tau, would be extremely useful. Patients with increased tau in the brain tend to exhibit AD symptoms while those with amyloid plaques do not always have clear signs, at least not immediately.
“We think that P-tau is probably a better measure because it’s much more closely related to symptoms of disease,” said Boxer.
Earlier this year, he and his colleagues published a study in Nature Medicine showing that P-tau181 is more than three times as high in individuals with AD compared with healthy elderly people. It also differentiated AD from FTD.
“We found that P-tau 181 was almost as good as a PET scan or lumbar puncture at identifying individuals with AD pathology in the brain,” said Boxer.
They next wanted to assess how well P-tau 217 held up as a possible biomarker.
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