A new blood test that detects a hallmark of Alzheimer's is poised to change the way doctors diagnose and treat the disease.
The test, the first of its kind to be cleared by the Food and Drug Administration, is for people 55 and older who already have memory problems or other signs and symptoms of Alzheimer's.
The results show whether the brain of a person with cognitive symptoms also has amyloid plaques, clumps of toxic proteins that build up in the spaces between brain cells. The presence of plaques in a person with cognitive symptoms usually confirms an Alzheimer's diagnosis.
"I think the blood test is going to really revolutionize the way people with Alzheimer's are cared for and diagnosed," says Dr. Howard Fillit, chief science officer at the Alzheimer's Drug Discovery Foundation.
"Primary care physicians will now have access to something that can give them a quicker read" on whether a patient has Alzheimer's, says Maria Carrillo, chief science officer of the Alzheimer's Association.
One benefit of a readily-available blood test will be more accurate diagnoses, Fillit says, noting that currently, primary care doctors correctly diagnose patients only about 60% of the time.
"Specialty neurologists get it right like seventy, eighty percent of the time," He says. "With the blood test, we can get it up to over 90%."
A PET scan is the gold standard for detecting the amyloid plaques associated with Alzheimer's. But the technology is costly, and unavailable in many communities.
Another option is to test fluid from a spinal tap, an invasive procedure that most doctors and patients tend to avoid.
There are already lab-developed blood tests that can signal the presence of amyloid. But the Lumipulse assay, made by the diagnostic company Fujirebio, is the first to receive marketing clearance from the FDA.
Having such a test is likely to mean that many more people will be diagnosed when their symptoms are still mild, and potentially treatable.
A survey from the Alzheimer's Association found that the vast majority of older Americans would take a blood test to find out if they have the disease.
People who are diagnosed while still in the early stages of Alzheimer's may be eligible to receive one of the two amyloid-reducing drugs now on market.
Lab-developed blood tests have been used primarily by researchers, or by specialists in large medical centers. The test cleared by the FDA is likely to attract a much broader audience.
"It's been through rigorous evaluation, and it provides guidance for prescribers on who's eligible and when the test should be provided," Carrillo says.
The result should be more testing of people in rural or underserved areas.
"Blood tests have given us an opportunity to really democratize this kind of testing," Carrillo says.
It also means that many more of the estimated 7.2 million Americans thought to be living with Alzheimer's are likely to get a formal diagnosis.
To help health health care providers counsel these individuals, the Alzheimer's Association is writing guidelines on how to speak to patients about the results of a blood test, what it means to live with the disease, and what the treatment options are.
The guidelines are expected this summer.
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