Blood tests can more accurately detect Alzheimer’s disease than other available methods used by doctors, according to results of a study presented recently at the Alzheimer’s Association International Conference 2024 in Philadelphia.
This could soon make it simpler and quicker for doctors in Florida to diagnose this common brain disorder. One that's a growing public health crisis, according to the Alzheimer’s Association, which estimates that 580,000 people 65 years of age and older live with it in the state. That number is expected to increase in the future.
Miami-Dade County leads the nation with the highest rate of Alzheimer's within that age group.
Blood biomarker study
Researchers in Sweden included more than 1,200 patients with cognitive symptoms in their study, testing them for key proteins in the blood known as a biomarker of Alzheimer’s disease. One of them is phosphorylated tau217 or pTau217.
These proteins form into tangles and are one of the defining features of Alzheimer’s disease in the brain. Tau tangles in neurons is linked to cognitive decline because they lead brain cell death.
Someone who has pTau buildup will typically also have abnormal levels of amyloid in the brain.
Beta-amyloid protein clumps form plaques that block cell-to-cell signaling in the brain that would normally take place. As neurons stop working and die, the brain shrinks over time and it loses most of its functions.
The blood test used in the study is called an amyloid probability score 2 test, or APS2. Between February 2020 and January 2024, researchers found that among 698 patients at memory clinics, the APS2 test was about 90% accurate at identifying Alzheimer’s disease. Specialists were 73% accurate.
Then among 515 patients seen in primary care, APS2 was around 90% accurate while primary care physicians were 63% accurate at identifying Alzheimer’s.
These findings were also published in the JAMA medical journal.
What's next
Blood testing for Alzheimer’s doesn’t have approval yet from the U.S. Food and Drug Administration, which doesn't mean clinicians can't use them, but they're expensive.
When it gets FDA approval, blood biomarker tests for Alzheimer's will be covered by Florida Medicaid and state insurance plans. A new state law will require Florida Medicaid and state insurance plans to cover biomarker tests, starting Jan. 1.
A biomarker, such as a certain gene or protein, is found in the blood, body fluids or other tissues that indicate a sign of a condition or disease.
Alzheimer’s has no cure or reversal, but getting an early diagnosis helps people become eligible for the drugs currently available: lecanemab, sold under the brand name Leqembi, and donanemab, sold as Kisunla, which have been proven effective in slowing cognitive decline down.
To participate in Alzheimer’s clinical trials, one also needs to have an early diagnosis. Once a patient is in the middle stages of this disease, it's too late for treatment or trials.
“Think of all the colleges that are staffed in Florida — every individual under that state plan will be able to have their biomarker covered by the state of Florida,” said Stefanie Wardlow, a senior program manager at the Alzheimer's Association in Florida. “This is definitely going to be a paradigm shift in terms of how people can get diagnosed. A more accurate and earlier diagnosis for Alzheimer’s disease is needed, and blood biomarkers will pave the way for that.”
Accurate diagnoses remain essential
Currently, making an Alzheimer’s diagnosis could involve various processes — exams, cognitive testing, basic labs, brain scans and others to rule out depression or a vitamin deficiency that could also impact memory.
Typically, a specialist will get a history from a patient and also speak to a family member, he or she could also have a patient get an MRI, a spinal fluid test or PET scan.
“Blood tests are always quicker, easier, and cheaper to do, but they still require a knowledgeable specialist to be able to interpret the results and communicate them accurately and sensitively to patients and care partners,” wrote Dr. Marc Agronin, a geriatric psychiatrist and chief medical officer at the Frank C. and Lynn Scaduto MIND Institute at Miami Jewish Health.
“Not every positive blood test confirms Alzheimer’s disease, and so this very consequential diagnosis must be made in a very careful way. The risk of getting blood tests without understanding the full context is the potential misdiagnosis of the disease, unnecessarily scaring patients.”
The U.S. has a shortage of neurologists, so sometimes people face long waits to get an appointment. These blood tests, once FDA approved, may help people get access to treatment sooner if their primary physician will be skilled in interpreting the results of an accurate blood test.
“If you can make the diagnosis, then you can get people into treatment faster,” said Dr. James E. Galvin, a professor of neurology at the University of Miami Miller School of Medicine and the founder and director of UM’s Comprehensive Center for Brain Health. “Whereas if you refer a person to the neurologist for the diagnosis, there's a long wait to see a neurologist. I think the blood test is going to quicken the path for a lot of people to be diagnosed and treated."
Galvin said biomarker tests will show doctors whether there's some specific pathology changes in the brain, and they need to interpret those changes in the context of the patient's symptoms to make the right diagnosis.
For more information, call the Alzheimer’s Association helpline at 1-800-272-3900.
