Estimated read time: 4-5 minutes
This archived news story is available only for your personal, non-commercial use. Information in the story may be outdated or superseded by additional information. Reading or replaying the story in its archived form does not constitute a republication of the story.
ATLANTA — Testing a person's blood for a type of protein called phosphorylated tau, or p-tau, could be used to screen for Alzheimer's disease with "high accuracy," even before symptoms begin to show, a new study suggests.
The study involved testing blood for a key biomarker of Alzheimer's called p-tau217, which increases at the same time as other damaging proteins — beta amyloid and tau — build up in the brains of people with the disease. Currently, to identify the buildup of beta amyloid and tau in the brain, patients undergo a brain scan or spinal tap, which often can be inaccessible and costly.
But this simple blood test was found to be up to 96% accurate in identifying elevated levels of beta amyloid and up to 97% accurate in identifying tau, according to the study published Monday in the journal JAMA Neurology.
"What was impressive with these results is that the blood test was just as accurate as advanced testing like cerebrospinal fluid tests and brain scans at showing Alzheimer's disease pathology in the brain," Nicholas Ashton, a professor of neurochemistry at the University of Gothenburg in Sweden and one of the study's lead authors, said in an email.
The study findings came as no surprise to Ashton, who added that the scientific community has known for several years that using blood tests to measure tau or other biomarkers has the potential to assess Alzheimer's disease risk.
"Now we are close to these tests being prime-time and this study shows that," he said. Alzheimer's disease, a brain disorder that affects memory and thinking skills, is the most common type of dementia, according to the National Institutes of Health.
Blood test 'definitive' in 80% of participants
The study included data on 786 people, who had an average age of 66 and had brain scans and spinal taps completed, as well as blood samples collected.
Some of the participants showed signs of cognitive decline while undergoing the data collection but others did not. The researchers, from institutions in Sweden, the United States and other countries, analyzed the participants' data from February to June of last year.
The researchers found that when they tested a participant's blood sample with the p-tau217 immunoassay, the blood test showed similar results and accuracies in identifying abnormal beta amyloid and tau as the results from the participant's spinal tap or brain scan.
Only about 20% of the study participants had blood test results that, in a clinical setting, would have required further testing with imaging or a spinal tap due to being unclear.
"This is a significant reduction in costly and high-demand examinations," Ashton said in the email. Therefore, based on the study findings, "we think that a blood test and clinical examination can have definitive decision in 80%" of those who are being investigated for early signs of dementia.
Yet even though the blood test in this study was found to be highly accurate in predicting whether someone has key characteristics of Alzheimer's disease in their brain, not everyone with those characteristics will go on to develop the disease.
'Keep Alzheimer's under better control'
Also, the p-tau test is specific for Alzheimer's disease, so if someone tests negative but is showing signs of cognitive impairment, this test could not determine other possible causes of their symptoms, such as vascular dementia or Lewy body dementia.
"A blood test being negative speeds up the investigation for other causes of the symptoms and this is just as important," Ashton said.
Signs and symptoms of Alzheimer's disease can vary from one person to another, but often memory problems are the first signs of the disease, such as losing track of dates, getting lost, misplacing things or having difficulty completing tasks, such as bathing, reading or writing.
Dr. Richard Isaacson, director of research at the Institute for Neurodegenerative Diseases in Florida, who was not involved in the study, has researched blood biomarkers in people with no or minimal cognitive complaints, likened testing blood samples for signs of Alzheimer's disease to how people undergo routine blood tests for high cholesterol.
"People get cholesterol tests before they have a heart attack. People get cholesterol tests before they have a stroke. To me, this type of test will eventually be best served in people before they start to have cognitive symptoms," Isaacson said. And "just like cholesterol tests, by following the pTau217 level over time, we can better understand how various therapies and lifestyle changes are working to keep Alzheimer's under better control."
