Alzheimer's disease blood test could provide faster diagnosis, new study says

A blood test for biological markers of Alzheimer’s disease could open the way for faster, cheaper diagnoses, according to a new study.

"A blood test could identify patients much earlier on," said Dr. Nikhil Palekar, director of the Stony Brook Center of Excellence for Alzheimer's Disease and of the medical center’s Alzheimer’s Disease Clinical Trials Program.

As research into Alzheimer’s treatment advances, Palekar, a board member of the Alzheimer's Association’s Long Island Chapter, said: "If we can find patients who have no cognitive symptoms and treat them early enough, it’s reasonable that we can completely stop the symptoms from developing."

Blood test for biomarkers

Researchers found the blood test for the biomarkers was around 90% accurate in identifying Alzheimer’s, while without using it, specialists were 73% accurate and primary care physicians 63%. The research, funded in part by the Alzheimer’s Association, is published in the Journal of the American Medical Association.

Early diagnosis is the Holy Grail of Alzheimer’s research because, in theory, treatment could halt the irreversible, fatal disease before it causes brain damage. There is no cure for Alzheimer’s, but there are medications to manage its effects and slow cognitive decline in people with the disease. They are only approved for use in patients with early-stage Alzheimer’s and may carry safety risks of their own.

The United States Food and Drug Administration on July 2 approved one of them, donanemab. Last year it approved a related drug, lecanemab. It also approved a related drug, aducanumab, which is no longer being marketed. They belong to a class of drugs known as anti-amyloids that have shown modest but statistically significant effects in slowing progression of the disease.

Widespread use of a blood test for Alzheimer’s could be also be a boon for researchers if it expands the pool of asymptomatic patients for clinical trials, Palekar said. It could also help doctors better stratify patients with cognitive complaints, flagging those who tested positive for fast follow-up by specialists, a wait that can now take up to nine months, Palekar said.

Living with Alzheimer's

"This is a real issue for Long Island," he said. "The big problem is how we are going to diagnose patients."

Alzheimer's Association researchers estimate there are close to 62,000 Long Islanders living with Alzheimer's, a number that could grow as the region skews older. 

Dr. Sebastian Palmqvist, a researcher at Lund University in Sweden, was the study’s lead author. Another Lund researcher, Dr. Oskar Hansson, was senior author. The study followed 1,213 patients: 515 in primary care with a median age of 77, and 698 in specialist care at memory clinics with a median age of 74, the two wrote in an email. 

The patients were tested with the blood test, PrecivityAD2, that measures proteins that are known biomarkers for Alzheimer’s disease. The test is available across most of the United States but not yet in New York State, which has its own certification process, according to the test’s manufacturer, C2N Diagnostics.

The standard work-up used by doctors in the study included cognitive testing, CT scans and clinical evaluation; the specialists’ cognitive tests and evaluations were more comprehensive.

The researchers used diagnosis by cerebrospinal fluid biomarkers as their gold standard to measure accuracy. 

The blood test, which hit the market in 2020, costs $1,450, though the company offers a financial assistance program that can lower the price. It is not universally covered by private insurance or Medicare, though the company says research shows its test was associated with a cost savings of $643 per Alzheimer's disease case. 

Real-world usefulness

Palmqvist and Hansson said their study suggested the blood test could have real-world usefulness. "We had ‘theoretical’ knowledge of the great potential of such a test based on research-based, selected cohorts," Palmqvist and Hansson wrote. "However, we had no idea how it would perform when tested as part of clinical practice."

Hansson, in a news release accompanying the results, said the researchers saw their findings as "a major step toward global clinical implementation of an Alzheimer’s blood test."

Columbia University neurologist Dr. Lawrence Honig, an Alzheimer’s expert, said the findings suggested blood testing could be useful, to a point. In people with symptoms, doctors would not likely treat Alzheimer’s disease simply on the basis of a positive blood test without also testing spinal fluid or ordering a PET scan, he said.

Also, while blood testing offers advantages for widespread application — it is relatively noninvasive and a blood draw can be done by a phlebotomist — "very few would argue to perform this test on asymptomatic persons unless we have proven treatment for asymptomatic individuals," which science does not yet have.

One expert was skeptical. "If you, like me, don’t think this is going to make a significant impact on the quality of life for people with this disease, this is putting the cart before the horse," said Dr. Jeremy Koppel, co-director of the Litwin-Zucker Center for the Study of Alzheimer's Disease at the Feinstein Institutes for Medical Research at Northwell Health. "It only really matters if you can send somebody for treatment."

Slowing progression

The current crop of anti-amyloids "marginally slow the rate of progression" of Alzheimer’s, Koppel said. They also come with a risk of brain bleeds and are costly, he said. Drugmaker Eli Lilly priced donanemab, marketed as Kisunla, at $32,000 per year. The company says patients' out-of-pocket cost for treatment will depend on their length of treatment and their insurance, though the drug is Medicare-eligible.

If improved diagnostic accuracy does have any immediate benefit, it may be more social than strictly medical, Koppel said. "People do want to know what’s wrong with them, and their families want to know, insofar as it may be important to think about what the future holds, why they are having trouble remembering things, and what kind of planning needs to take place."

Ira and Sheryl Kleiner, of Middle Island, said a rapid, accurate blood test might have helped them. They said doctors in 2016 told Ira Kleiner, 72, a retired optician, that he might have Alzheimer’s. It took almost half a year before a PET scan revealed the cause of his occasional bouts of disorientation and short term memory loss was not Alzheimer’s, but a combination of frontotemporal lobe dementia and vascular dementia.

Those conditions, like Alzheimer’s, are incurable, but Kleiner said faster diagnosis might have let him keep working longer at a job he loved rather than taking the time for medical tests. 

"I was on medical leave for almost a year to find out what the hell was going on with me," he said. "To be away from something that I loved to do — I’m a people person and I love that interaction — that was devastating to me."