WASHINGTON (AP) — New blood tests could help doctors diagnose Alzheimer’s disease faster and more accurately, but some appear to work much better than others, researchers reported Sunday.
It’s hard to tell if memory problems are caused by Alzheimer’s. That requires a hard-to-obtain brain scan or an uncomfortable spinal tap to confirm the buildup of a sticky protein called beta-amyloid, one of the hallmarks of the disease. Instead, many patients are diagnosed based on symptoms and cognitive exams.
Labs have begun offering a variety of tests that can detect specific signs of Alzheimer’s in the blood. Scientists are excited about their potential, but the tests are not yet widely used because there is little data to guide doctors on which type to order and when. The U.S. Food and Drug Administration has not approved any of them, and insurance coverage is sparse.
“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 issue. While some are very accurate, “other tests are not much better than flipping a coin.”
Demand for earlier diagnosis of Alzheimer’s is increasing
More than 6 million people in the United States and millions more worldwide have Alzheimer’s, the most common form of dementia. Its telltale “biomarkers” are amyloid plaques, which clog the brain, and abnormal tau protein, which leads to neuron-killing tangles.
The new drugs Leqembi and Kisunla can modestly slow the worsening of symptoms by clearing sticky amyloid from the brain. But they only work in the earliest stages of Alzheimer’s, and it can be difficult to prove that patients qualify in time. Measuring amyloid in spinal fluid is invasive. A special PET scan to detect plaques is costly and can take months to get an appointment.
Even experts can have difficulty telling whether a patient’s symptoms are caused by Alzheimer’s or something else.
“Very often I have patients who I believe have Alzheimer’s disease and I get tested and the results come back negative,” Schindler said.
Blood tests for Alzheimer’s could be simpler and faster, new study suggests
Blood tests have so far been used mostly in carefully controlled research settings. But a new study of nearly 1,200 patients in Sweden suggests they can also work in the real-world hustle and bustle of doctors’ offices — particularly primary care doctors, who see people with memory problems far more often than specialists but have fewer tools to evaluate them.
In the study, patients who presented to a primary care physician or specialist with memory complaints were given an initial diagnosis using traditional exams, had blood drawn for testing, and were sent for confirmatory spinal fluid or brain scans.
The blood test was much more accurate, Lund University researchers reported Sunday at the Alzheimer’s Association International Conference in Philadelphia. Primary care doctors’ initial diagnoses were 61% accurate, while specialists’ were 73% accurate — but the blood test was 91% accurate, according to the findings, which were published in the Journal of the American Medical Association.
What blood tests are best for Alzheimer’s disease?
Dr. John Hsiao of the National Institute on Aging said it’s almost a “wild west” in the variety offered. They measure different biomarkers in different ways.
Maria Carrillo, chief scientific officer for the Alzheimer’s Association, said doctors and researchers should use only blood tests that have been proven to have an accuracy rate of more than 90 percent.
Carrillo and Hsiao agreed that today’s tests were most likely to meet a criterion called p-tau217. Schindler led an unusual direct comparison of several blood tests, funded by the National Institutes of Health Foundation, that came to the same conclusion.
Schindler explained that such tests measure a form of tau that measures how much plaque buildup a person has. A high level indicates a person is likely to have Alzheimer’s, while a low level indicates it is probably not the cause of memory loss.
Several companies develop p-tau217 tests, including ALZpath Inc., which provided the version used in the Swedish study, Roche, Eli Lilly and C2N Diagnostics.
Who should get a blood test for Alzheimer’s?
Only doctors can order them from labs. The Alzheimer’s Association is working on guidelines, and several companies are looking to seek FDA approval, which would clarify appropriate use.
For now, doctors should only use blood tests on people with memory problems, Carrillo said, and only after checking the accuracy of the type they want.
“It really has great potential, especially for primary care physicians, to help them determine who to give reassuring messages to and who to refer to memory specialists,” said Dr. Sebastian Palmqvist of Lund University and Dr. Oskar Hansson of Lund University, who led the study in Sweden.
Schindler emphasized that testing is not yet available for people who do not yet have symptoms but are concerned that Alzheimer’s disease runs in their family, but that this is within the scope of participation in research studies.
That’s partly because amyloid buildup can begin two decades before the first signs of memory problems, and so far there have been no preventive measures beyond basic advice like eating healthy, exercising and getting enough sleep. But studies are ongoing to test possible treatments for people at high risk of Alzheimer’s, and some involve blood tests.
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The Associated Press Health and Science Department receives support from the Howard Hughes Medical Institute’s Science and Education Media Group. The AP is solely responsible for all content.