It can take months or years for doctors to determine whether someone with early symptoms of memory loss has Alzheimer’s disease.
But experts say a new generation of blood test could replace the costly brain scans and spinal taps currently used to diagnose the mind-robbing disease. Early diagnosis could allow patients to get Food and Drug Administration-approved Alzheimer’s drugs sooner. The new blood test could also help drug researchers more efficiently conduct clinical trials evaluating experimental drugs aimed at slowing the progression of the incurable disease that afflicts 6.9 million Americans.
This week, researchers at the Alzheimer’s Association International Conference will present the results of a series of studies evaluating these new blood tests. Although the blood tests are not yet widely used in memory disorder clinics, new research suggests that some of the blood tests have proven accurate and may soon be widely used in medical practice.
“We know that blood tests can improve the accuracy of early diagnosis and potentially maximize a patient’s chances of receiving treatment for Alzheimer’s disease,” said Rebecca Edelmeyer, PhD, senior director of scientific affairs at the Alzheimer’s Association. “The field is really moving forward with the availability of these types of tests.”
Diagnosing the memory-robbing disease is not easy: Doctors must examine patients and administer tests of memory and thinking skills. After that, they may refer them to a specialist clinic for a PET scan or spinal tap to see if there is evidence of amyloid beta protein buildup that forms plaques in the brains of people with Alzheimer’s.
Blood test outperforms doctors in diagnosing Alzheimer’s
Research suggests a new blood test can accurately identify whether someone has Alzheimer’s. In a study of more than 1,200 patients with signs of Alzheimer’s, the Precivity AD2 blood test, which measures the ratio of tau to amyloid beta proteins, detected the disease more frequently than doctors did.
Among two large groups of patients who visited a specialized memory disorders clinic or a general practice clinic, the Precivity test accurately detected 90 percent of cases, even in patients with complex medical histories such as kidney disease, according to a study published Sunday in the Journal of the American Medical Association. By comparison, specialists at memory disorders clinics identified 73 percent of cases, and general practice doctors correctly diagnosed 63 percent of cases.
Experts said they were encouraged by the finding that the blood test could improve diagnostic accuracy for a wide range of doctors, including specialists and primary care physicians. Many patients may not have access to memory clinics or specialized tests such as PET scans, which visually detect amyloid-beta plaques, or spinal taps, which take a sample of cerebrospinal fluid.
“The big hope for blood testing is that it will eventually become accessible and hopefully cost-effective and non-invasive,” Edelmeyer said.
The PrecivityAD2 test uses a technology called mass spectrometry to measure the ratio of phosphorylated tau and beta-amyloid proteins to determine whether a patient has the disease. The test is manufactured by St. Louis-based C2N Diagnostics, which mails test kits to doctors and researchers, who then send samples back to the company’s lab to run the tests.
The company is allowed to sell the test under Food and Drug Administration regulations because the tests are done in its laboratories, which are certified under the Clinical Laboratory Improvement Amendments to federal testing law, known as CLIA. The Mayo Clinic also offers the test.
The list price is $1,450, and insurance plans typically don’t cover the test, so C2N officials say their first priority is building scientific evidence and working with insurance companies to get formal coverage.
The PrecivityAD2 test is one of dozens of diagnostics being developed and evaluated by researchers. Another testing company, ALZpath, has licensed its technology to large commercial companies such as Roche and Beckman Coulter. ALZpath’s goal is to widely deploy its proprietary tau test through its commercial testing platform, which is already in use in hospitals and other medical settings.
“We believe this will completely change the way Alzheimer’s disease is diagnosed, and it will be driven by therapies that are now becoming available,” said Chad Holland, CEO of ALZpath.
Blood test could detect illness before memory and thinking problems emerge
Another study published Sunday found that a blood test for tau could identify people who are likely in the early stages of the disease, even if they show no signs of memory or thinking problems.
Researchers from Lund University in Sweden analyzed samples from more than 2,700 cognitively normal people across 10 studies. The samples included both tau in the blood and amyloid beta detected by PET scans or spinal taps. The studies concluded that tau testing could predict 79-86% of cases of amyloid beta buildup detected by PET scans or spinal taps in cognitively normal people.
If the findings are confirmed, the researchers said, it could mean that a tau blood test could reduce the need for specialists to perform expensive PET scans and spinal taps to test patients for Alzheimer’s medical research.
“Our findings support that p-tau217 positivity in plasma alone may be sufficient to select amyloid-positive participants without cognitive impairment in many clinical trials,” said Gemma Salvado, lead author of the study and associate researcher at Lund University.
Faster access to Alzheimer’s drugs
Experts predict that older Americans will start requesting these blood tests as new Alzheimer’s treatments come on the market.
Earlier this month, the FDA approved Eli Lilly’s Alzheimer’s drug donanemab, which studies have shown can slow the early stages of the disease. Sold under the brand name Xanla, the drug is an antibody that removes beta-amyloid buildup in the brains of people with Alzheimer’s. Clinical studies have shown that people with mild Alzheimer’s disease experienced a 35% reduction in cognitive decline compared to those taking a placebo.
The FDA last year approved Eisai and Biogen’s drug Lukembi, which also helps slow cognitive decline in people in the early stages of the disease.
People in the early stages of the disease must be tested to confirm they have amyloid-beta before they can be prescribed these new drugs. But experts say these tests are often delayed or administered unevenly because of a shortage of Alzheimer’s specialists and because many people can’t get to clinics that can do PET scans or spinal taps to detect amyloid-beta.
Research to be presented at the conference says tau blood tests could enable primary care physicians to diagnose the disease more efficiently, shortening the wait time for patients to access new Alzheimer’s medications. Before these tests, doctors relied on cognitive testing and referred patients to specialists when necessary. With a shortage of specialists and limited capacity to perform tests with PET scans and spinal taps, patients must wait, sometimes months or years, to find out whether they have Alzheimer’s or another debilitating disease.
As the number of aging Americans grows, experts say there is an ever-increasing need for faster diagnoses. Without a blood-test diagnosis, by 2033, people will wait an average of nearly six years to find out if they can take Alzheimer’s medication, according to a study presented at the Alzheimer’s Association conference this week. But if primary care doctors were to run blood tests to rule out Alzheimer’s, that could shorten the wait to see a specialist. A University of Southern California-led study projects that the average wait time to get a diagnosis could fall to 13 months.
Edelmeyer said the Alzheimer’s Association plans to update its guidance for doctors and researchers on the appropriate use of blood tests for Alzheimer’s this week. When the guidance was last updated in 2022, the Alzheimer’s Association said these blood tests are valuable for research, but that memory clinics should be cautious in using them. The association also said the tests should not be used to broadly screen the population or sold directly to consumers.
Blood tests have become standard in academic research, said Nicholas Ashton, a neuroscientist at Banner Health in Phoenix, and he expects they will become more widely available in clinical settings at lower cost and with “rapid advances.”
“This is exactly where we need to be,” Ashton said.
Ken Alltucker is @kalltucker at X. Contact him by email at alltuck@usatoday.com.
This article originally appeared on USA TODAY: Blood test for Alzheimer’s could speed treatment for many Americans
