A new blood test designed to diagnose Alzheimer’s disease may make it easier for patients to get the treatment they need. The U.S. Food and Drug Administration approved the test, called the Lumipulse G pTau217/ß-Amyloid 1-42 Plasma Ratio, for patients 55 and older who are showing signs of Alzheimer’s.
How is Alzheimer’s diagnosed?
It is estimated that 7 million people in the U.S. live with dementia, and over 70% of them have Alzheimer’s disease. Alzheimer’s disease is a form of dementia that often results in difficulty forming new memories and progressive neurocognitive decline. One cause of Alzheimer’s disease is accumulation of amyloid plaque in the brain. Patients typically first begin to experience symptoms such as forgetfulness, memory loss, confusion and trouble with everyday tasks.
“Doing a clinical exam, you can get a diagnosis, which tells you that there is a cognitive impairment, but it doesn't tell you what's causing the problem. About 70% of people with amnestic dementia have Alzheimer’s disease” said Sayed Azizi, MD, PhD, Yale Medicine clinical chief of neurodegenerative disorders and professor of Neurology at Yale School of Medicine. “Then we can go and look at the brain to see if it’s because of Alzheimer’s. Now tests include a brain PET scan, which is called amyloid PET. The other test is a lumbar puncture, where you take fluid from around the brain and send it to the laboratory for analysis.”
The new blood test is unique in that it can measure proteins that would point to whether someone has plaque on the brain without the need for a scan or lumbar puncture.
“The blood test measures two proteins and their ratio. One protein is called P-Tau 217 and the other is AB 42. If the ratio is high, then the likelihood of the patient having Alzheimer’s disease is high. If the ratio is low, then the likelihood is low,” said Dr. Azizi.
The results are approximately 95% accurate.
Treatments for Alzheimer’s
Many patients who have Alzheimer’s may be eligible for medications that can scrub the plaque from the brain. It does not repair any damage that is already done, but it can maintain the brain as it is once the patient begins treatment.
The plaque-scrubbing treatments Lecanemab and Donanemab are both offered through Yale New Haven Health. Since they are administered via intravenous infusion, patients typically receive their treatment at an outpatient location every month or every two weeks for 18 months.
Some people can have a reaction to these medications. Scrubbing the plaque can result in swelling or rawness with small bleeds in the brain. Regularly scheduled MRIs would show if someone were having a reaction and then treatment would stop.
Older medications in the form of pills do not clean plaque but can boost memory for a short period of time.
Who is a good candidate for the Alzheimer’s blood test?
Any adult experiencing memory problems who receive a clinical evaluation and diagnosis of mild cognitive impairment would be a good candidate for the new blood test.
“This has the potential to be very useful. A primary care physician can do an exam and notice cognitive problems, orders the blood test and then sends the patient to a specialist to decide whether they should get the treatment” said Dr. Azizi. “If we confirm the diagnosis of Alzheimer’s, then they can be eligible for those medications.”
