US: A less invasive as well as cost-effective blood test has been developed by the researches from the National Institute of Ageing here which can diagnose Alzheimer's disease much early before their symptoms appear. The blood test detects the abnormal accumulation of tau protein known as phosphorylated-tau-181 (ptau181), which is a biomarker of Alzheimer's disease.
There are three typical hallmarks of Alzheimer's disease: plaques of beta-amyloid protein, tangles of tau protein, and loss of connections between brain cells.
Tau and other biomarkers can be detected with PET scans of the brain and lab tests of spinal fluid. However, PET imaging is expensive and involves radioactive agents, and spinal fluid tests require spinal taps, which are invasive, complex and time-consuming. Hence with this development of simple blood test, detection of the disease is made easy and reliable also.
Alzheimer's disease is a major cause of dementia that destroys brain cells and tissue. As the brain damage spreads, it leads to symptoms such as confusion, memory loss, and diminishing capacity to function. Eventually, the person can no longer lead an independent life. Hence there is an urgent necessity to derive at an early diagnosis.
"The considerable time and resources required for screening research participants with PET scans and spinal taps slow the pace of enrollment for Alzheimer's disease treatment studies," said Richard J. Hodes, M.D., director of NIH's National Institute on Aging (NIA), which funded much of the study. "The development of a blood test would enable us to rapidly screen a much larger and more diverse group of volunteers who wish to enroll in studies," he added.
An international team of researchers led by Adam Boxer, M.D., Ph.D., at the University of California, San Francisco, used the new test to measure the concentration of ptau181 in plasma. The samples were collected from more than 400 participants from the University of California, San Francisco Memory and Aging Center, part of the NIA-funded Alzheimer's Disease Research Center; the NIH-supported Advancing Research and Treatment for Frontotemporal Lobar Degeneration (ARTFL) consortium; and a research study by Eli Lilly.
Their study demonstrated that the ptau181 in plasma could differentiate healthy participants from those with Alzheimer's pathology, and differentiate those with Alzheimer's pathology from a group of rare neurodegenerative diseases known collectively as frontotemporal lobar degeneration (FTLD).
This may also help physicians to detect and diagnose Alzheimer's and related neurodegenerative disorders earlier when interventions are more likely to be effective.
In addition, they followed participants for several years and observed that high levels of plasma ptau181 among those who were cognitively normal or had mild cognitive impairment may be used to predict later development of Alzheimer's dementia. Their results have been published in Nature Medicine.
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Reference: Thijssen EH et al. Diagnostic value of plasma phosphorylated tau181 in Alzheimer's disease and frontotemporal lobar degeneration. Nature Medicine. March 2, 2020. doi: 10.1038/s41591-020-0762-2.
Janelidze S et al. Plasma P-tau181 in Alzheimer's disease: relationship to other biomarkers, differential diagnosis, neuropathology and longitudinal progression to Alzheimer's dementia. Nature Medicine. March 2, 2020. doi: 10.1038/s41591-020-0755-1.