WASHINGTON – New blood tests could help doctors diagnose Alzheimer’s disease more quickly and accurately, researchers reported Sunday — but some appear to work much better than others.
It’s difficult to know whether memory problems are caused by Alzheimer’s disease. This requires confirmation from one of the characteristic signs of the disease – buildup of a sticky protein called beta-amyloid – with a hard-to-get brain scan or an uncomfortable lumbar puncture. Many patients are diagnosed based on symptoms and cognitive exams.
Laboratories have begun offering a variety of tests that can detect certain signs of Alzheimer’s disease in the blood. Scientists are excited about its potential, but the tests are not yet widely used because there is little data to guide doctors about what type to order and when. The U.S. Food and Drug Administration has not formally approved any of them, and there is little insurance coverage.
“What tests can we trust?” asked Dr. Suzanne Schindler, a neurologist at Washington University in St. Louis who is part of a research project examining this. While some are very accurate, “other tests are not much better than flipping a coin.”
More than 6 million people in the United States and millions more around the world have Alzheimer’s, the most common form of dementia. Its telltale “biomarkers” are amyloid plaques that clog the brain and abnormal tau protein that leads to neuron-killing tangles.
New drugs, Leqembi and Kisunla, may modestly slow the worsening of symptoms by removing sticky amyloid from the brain. But they only work in the early stages of Alzheimer’s disease and it can be difficult to prove patients qualify in time. Measuring amyloid in spinal fluid is invasive. A special PET scan to detect plaque is expensive, and getting an appointment can take months.
Even experts can have difficulty knowing whether Alzheimer’s or something else is to blame for a patient’s symptoms.
“It’s not uncommon for me to have patients who I’m convinced have Alzheimer’s disease and I get tested and it comes back negative,” Schindler said.
Until now, blood tests have mainly been used in carefully controlled research settings. But a new study of about 1,200 patients in Sweden shows that they can also work in the real hustle and bustle of doctors’ offices — especially primary care doctors who see far more people with memory problems than specialists but have fewer tools to evaluate them. them.
In the study, patients who visited a primary care doctor or specialist for memory complaints got an initial diagnosis through traditional testing, donated blood for testing, and were referred for a confirmatory lumbar puncture or brain scan.
The blood tests were much more accurate, Lund University researchers reported Sunday at the Alzheimer’s Association International Conference in Philadelphia. The primary care doctors’ initial diagnosis was 61% accurate and the specialists’ 73% — but the blood test was 91% accurate, according to the results, which were also published in the Journal of the American Medical Association.
There’s almost “a Wild West” in the variety on offer, said Dr. John Hsiao of the National Institute on Aging. They measure different biomarkers, in different ways.
Doctors and researchers should only use blood tests that have been shown to have an accuracy rate greater than 90%, said Maria Carrillo, chief scientific officer at the Alzheimer’s Association.
Today’s tests most likely to meet this benchmark measure are called p-tau217, Carrillo and Hsiao agreed. Schindler helped conduct an unusual head-to-head comparison of several types of blood tests, funded by the Foundation for the National Institutes of Health, that reached the same conclusion.
This type of test measures a form of tau that correlates with the amount of plaque accumulated in someone, Schindler explained. A high level indicates a high probability that the person has Alzheimer’s, while a low level indicates that this is probably not the cause of the memory loss.
Several companies are developing p-tau217 tests, including ALZpath Inc., Roche, Eli Lilly and C2N Diagnostics, which provided the version used in the Swedish study.
Only doctors can order them from laboratories. The Alzheimer’s Association is working on guidelines and several companies plan to seek FDA approval, which would clarify proper use.
For now, Carrillo said doctors should only use blood tests on people with memory problems after verifying the accuracy of the type requested.
Especially for primary care doctors, “it really has great potential to help them decide who to give a reassuring message to and who to send to memory specialists,” said Dr. Sebastian Palmqvist of Lund University, who led the Swedish study. with Lund’s doctor. Dr Oskar Hansson.
The tests are not yet for people who don’t have symptoms but are concerned about Alzheimer’s in their family — unless that’s part of enrolling in research studies, Schindler stressed.
This is in part because amyloid buildup can begin two decades before the first sign of memory problems, and to date, there are no preventive measures beyond basic advice for eating healthy, exercising and getting enough sleep. But there are ongoing studies testing possible therapies for people at high risk of Alzheimer’s, and some include blood tests.
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