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A company has started selling the first blood test to help diagnose Alzheimer’s disease, a leap in the field that could help people know if they have dementia. It also raises concerns about the accuracy and impact of this life-changing news.
Independent experts are suspicious because key test results have not been released and the test has not been approved by the United States Food and Drug Administration – it is sold under more general rules for laboratories commercial. But they agree that a simple test that can be done in a doctor’s office is long overdue.
It might have saved Tammy Maida a decade of futile trips to doctors who attributed her symptoms to depression, anxiety or menopause before a $ 5,000 brain scan last year finally showed. that she had Alzheimer’s disease.
“Now I have an answer,” said the 63-year-old nurse from San Jose, Calif.
If a blood test had been available, “I might have been afraid of the results,” but I would have “jumped on it” to find out, she said.
More than 5 million people in the United States and millions more around the world have Alzheimer’s disease, the most common form of dementia. To be diagnosed, people must have symptoms such as memory loss and evidence of a buildup of a protein called beta-amyloid in the brain.
The best way to measure protein now is with an expensive PET brain scan which is usually not covered by insurance. This means that most people don’t have one and wonder if their problems are due to normal aging, Alzheimer’s disease, or something else.
The C2N Diagnostics blood test in Saint-Louis aims to fill this gap. The founders of the company include Drs. David Holtzman and Randall Bateman of Washington University School of Medicine, who led the research that led to the test and are included in a patent that the University of St. Louis cleared to C2N.
About the test
The test is not intended for general screening or people without symptoms – it is for people 60 years and older who have thinking problems and who are being evaluated for Alzheimer’s disease. It is not covered by insurance or Medicare; the company charges $ 1,250 and offers discounts based on income. Only doctors can order the test and the results are delivered within 10 days. It is sold in almost every state in the United States and has just been cleared for sale in Europe.
It measures two types of amyloid particles as well as various forms of protein that reveal whether someone has a gene that increases their risk for disease. These factors are combined into a formula that includes age, and patients are given a score suggesting a low, medium, or high likelihood of amyloid accumulation in the brain.
If the test puts them in the low category, “that’s a good reason to look for something else” besides Alzheimer’s disease, Bateman said.
“There are a thousand things that can cause cognitive impairment,” from vitamin deficiencies to medication, Holtzman said.
“I don’t think it’s any different from the tests we’re doing now,” except it’s from a blood test rather than a brain scan, he said. “And these aren’t 100% accurate either.”
Is it correct?
The company has not released any data on the accuracy of the test, although doctors have published on amyloid research leading up to the test. The company’s promotional materials cite results comparing the test to PET brain scans – the current gold standard – in 686 people, aged 60 to 91, with cognitive impairment or dementia.
If a PET scan showed amyloid buildup, the blood test also gave a high probability 92% of the time and missed 8%, said company chief executive Dr. Joel Braunstein.
If the PET scan was negative, the blood test ruled out amyloid buildup 77 percent of the time. The remaining 23% tested positive, but that doesn’t necessarily mean the blood test was incorrect, Braunstein said. Published research suggests that it can detect amyloid buildup before it’s evident on scans.
Braunstein said the company will seek FDA approval and the agency has given it a designation that may expedite review. He said the results of the study would be released and he defended the decision to start selling the test now.
“Should we hold back this technology when it could have a big impact on patient care?” He asked.
Dr Eliezer Masliah, head of neuroscience at the US National Institute on Aging, said the government has funded some of the work leading up to the test as well as other types of blood tests.
“I would be careful to interpret any of these things,” he said of the company’s claims. “We are encouraged, we are interested, we are funding this work but we want to see results.”
Heather Snyder of the Alzheimer’s Association said she would not approve a test without FDA approval. The test should also be studied in larger and diverse populations.
“It’s not clear how precise or generalizable the results are,” she says.
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