WASHINGTON (AP) – New blood tests could help doctors diagnose Alzheimer’s disease more quickly and more accurately, researchers reported Sunday – but some seem to work much better than others.
It is difficult to tell if memory problems are caused by Alzheimer’s. That requires confirming one of the disease’s hallmark symptoms — a sticky protein buildup called beta-amyloid — with a hard-to-find brain scan or an uncomfortable spinal tap. Instead many patients are diagnosed based on symptoms and cognitive exams.
Laboratories have begun offering various tests that can detect certain 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 about what to order and when. None of them are formally approved by the US Food and Drug Administration and there is little insurance coverage.
“What tests can we trust?” Dr. asked. Suzanne Schindler, a neuroscientist at Washington University in St. Louis is part of a research project that examines that. While some are very accurate, “other tests are not much better than coin flipping”.
The demand for earlier Alzheimer’s diagnosis 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 brain-clogging amyloid plaques and abnormal tau protein that lead to neuron-killing tangles.
New drugs, Leqembi and Kisunla, can moderately slow worsening symptoms by removing gunky amyloid from the brain. But they only work in the earliest stages of Alzheimer’s and it is difficult to prove patients in time. Measuring amyloid in spinal fluid is invasive. A special PET scan to find plaques is expensive and can take months to get an appointment.
Even specialists can struggle to tell if Alzheimer’s or something else is to blame for patients’ symptoms.
“I have patients that I’m often not sure have Alzheimer’s disease and I do a test and it’s negative,” Schindler said.
A new study suggests that blood tests for Alzheimer’s can be simpler and faster
Blood tests have so far been used mainly 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 world of doctors’ offices – especially primary care doctors who see far more people with memory problems than specialists but have fewer tools to evaluate them.
In the study, patients who visited a primary care physician or specialist for memory complaints received an initial diagnosis using traditional exams, gave blood for testing and were sent for a confirmatory spinal tap or brain scan.
A blood test was 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, also published in the Journal of the American Medical Association.
What blood tests for Alzheimer’s work best?
There is 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 proven to have an accuracy rate of more than 90%, said Alzheimer’s Association chief science officer Maria Carrillo.
Today’s tests are more likely to meet that benchmark measurement known as p-tau217, Carrillo and Hsiao agreed. Schindler helped conduct an unusual direct comparison of several types of blood tests, funded by the National Institutes of Health, that reached the same conclusion.
That type of test measures a type of tau that correlates with how much plaque a person has, Schindler explained. A high level indicates a strong likelihood that the person has Alzheimer’s and a low level indicates that it is unlikely to be the cause of memory loss.
Several companies are developing p-tau217 tests including ALZpath Inc., Roche, Eli Lilly and C2N Diagnostics, which supplied the version used in the Swedish study.
Who should use blood tests for Alzheimer’s?
Only doctors can order them from laboratories. The Alzheimer’s Association is working on guidelines and some companies plan to seek FDA approval, which would clarify proper use.
Until now, Carrillo said doctors should only use a blood test in people with memory problems, after checking the accuracy of the type they order.
Especially for primary care physicians, “it has great potential to help them decide who should give a positive message and who should be referred to memory specialists,” said Dr. Sebastian Palmqvist of Lund University, who led Lund’s Swedish study. Dr. Oskar Hansson.
The tests don’t yet exist for people who don’t have symptoms but are concerned about Alzheimer’s in the family — unless it’s part of enrollment in research studies, Schindler emphasized.
That’s partly because amyloid buildup can start twenty years before the first sign of memory problems, and so far there are no preventative steps other than basic advice about healthy eating, exercise and getting enough sleep. But studies are underway testing potential therapies for people at high risk of Alzheimer’s, and some of them include a blood test.
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The Associated Press Health and Science Section is supported by the Howard Hughes Medical Institute Science and Media Education Group. The AP is solely responsible for all matters.