Study finds blood test for Alzheimer's could detect 90% of early dementia cases

the study A study published in January found that a similar p-tau217 test could identify elevated levels of beta-amyloid with 96% accuracy and tau with 97% accuracy. The presence of beta-amyloid and tau tangles in the brain is Alzheimer's disease.

The new study combined the p-tau217 test with the amyloid 42/40 ratio, which measures two types of amyloid protein, another blood biomarker for Alzheimer's disease.

A combination of amyloid and tau testing, called the amyloid probability score, was the most predictive.

“By blood test used Family doctor's office“This works like a cholesterol test for Alzheimer's disease,” says Dr. Maria Carillo, chief science officer at the Alzheimer's Association.

“The p-tau 217 blood test has been found to be the most specific and most valid for Alzheimer's disease, so it appears to be the front-runner,” said Carillo, who oversees the association's research activities, including the new study.

Once thoroughly examined, A highly accurate blood test “could dramatically change how quickly we can run clinical trials and develop the next drugs for Alzheimer's disease,” she said. “This is truly a transformative time.”

The peptide p-tau217 is unique in that it can only be detected if amyloid plaques are present in the brain, Carillo said.

“Scientifically, what that means is that by measuring p-tau217, you're measuring neuronal damage by tau at a very early stage of Alzheimer's disease, when amyloid is already present,” she said.

“It doesn’t actually measure amyloid, but the tests show it’s there, and that’s backed up by objective PET (positron emission tomography). “We now have scans that can look at amyloid in the brain,” Carrillo says, “and it's a great indicator of Alzheimer's. If you don't have amyloid, you don't have Alzheimer's. But we know that if you have increased tau in the brain, that's a sign of another type of dementia.”

Tau tangles have also been implicated in several other diseases. Neurological disorders FTD, etc., or Frontal lobe dementiaIn FTD, tau tangles attack the brain's frontal lobes, causing changes in behavior and emotions and loss of executive functions like planning. Memory loss, if it occurs, doesn't occur until much later.

In Alzheimer's disease, tangles of tau protein build up in parts of the brain responsible for memory. Amyloid plaques Amyloid plaque plays a key role: Tiny clumps of plaque can collect in synapses and interfere with nerve cells' ability to communicate. Amyloid plaques can also overstimulate the immune system, causing inflammation and further damage to the brain.

Among the newest dementia medications are: Lecanemab and donanemabThese drugs target beta-amyloid and are thought to be less effective in patients with advanced tau pathology, experts say.

Amyloid deposits begin to build up in the brain decades before symptoms appear, Even in your 30s and 40sEarly diagnosis of cerebral amyloidosis may be crucial for preventive treatment with lifestyle modifications and drugs.

The study was published in the journal JAMA NeurologyThe study followed 1,213 people, with a mean age of 74, who underwent cognitive assessments at both primary care and specialist clinics in Sweden.

Each person's blood was tested using p-tau217 and the results were combined with a blood measurement of beta-amyloid 40/42 to create a final score.

“Using the 40:42 ratio in combination with p-tau217 improves the diagnostic accuracy of p-tau217,” said Dr. Richard Isaacson, director of research at the Florida Institute for Neurodegenerative Diseases and a preventive neurologist, who was not involved in the study.

The 90% accuracy of the combined blood test in this study was confirmed by a spinal fluid tap, which, along with an amyloid PET scan, is currently the only gold standard scientific method for diagnosing Alzheimer's outside of an autopsy. Experts say both tests are expensive, invasive and not readily available across the United States.

The blood test results were then compared to patient diagnoses made by family doctors and specialists in Sweden. The relatively low accuracy (61% and 73%) highlights how difficult it is for doctors to accurately identify Alzheimer's disease with the current tools: a short patient interview, simple cognitive tests, and computed tomography (CT) scans of the brain.

“In general, neither traditional pen-and-paper tests nor digital cognitive assessments are very accurate in identifying Alzheimer's disease specifically,” said study co-author Dr Oscar Hansson, professor and senior consultant in neurology at Lund University.

“Many other diseases and disorders can present with similar cognitive symptoms, potentially leading to misdiagnosis or overlooking the condition,” Hanson said in an email.

In fact, 20-30% of patients seen by specialists take medicine or have other medical conditions Can be imitated Hanson said illnesses that can affect cognitive function include Alzheimer's disease, vascular dementia, depression, thyroid disease, sleep apnea and even vitamin B12 deficiency.

If these similar symptoms weren't detected on initial screening, Carrillo said, people without Alzheimer's disease could end up clogging specialist waiting lists and appointment lists for spinal taps and amyloid PET scans.

By the time someone with true amyloid pathology sees a specialist, “they may be past the point where they can take the medications we have now, and that would be terrible,” she added.

Wait times are only going to get worse, according to a mathematical model based on the aging U.S. population: By 2033, people would be waiting an average of nearly six years to find out if they qualify for a new Alzheimer's treatment if their primary care physician only used current cognitive assessments to diagnose dementia, a new study found. The study was presented Sunday at the Alzheimer's Association International Conference 2024 in Philadelphia.

But if an accurate blood test were used, the waiting period could be shortened to between six and 13 months, by significantly reducing the number of people needing to see a specialist or undergo further testing, the study found.

But don't expect blood tests for Alzheimer's to become routine in your doctor's office anytime soon: More research is needed to verify the positive results shown in the study, and guidelines for physician use need to be established and distributed, as well as to educate doctors about possible nuances, Isaacson said.

“Nobody is more excited about these tests than I am, but blood tests for Alzheimer's aren't completely definitive yet,” he says. “If you get a positive result, you need to confirm it with a PET scan or spinal tap. If you get a negative result, it's reassuring, but if it's borderline, we don't know yet what it means.”

Meanwhile, research shows there are many actions people can take to prevent or slow cognitive decline, including regular exercise, following a Mediterranean diet, and treating vascular risk factors such as high blood pressure, high cholesterol, and diabetes.

“Our goal is to use only the highest quality blood tests to not only aid in the early diagnosis of Alzheimer's disease, but also to assess response to risk-reduction interventions,” Isaacson said. “These are very hopeful times.”