The U.S. Food and Drug Administration has approved PrecivityAD2, a new blood test designed to help doctors diagnose Alzheimer’s disease in adults with symptoms such as memory loss or impaired thinking. It is the first test of its kind approved for people age 40 and older. By comparison, the first Alzheimer’s blood test approved in the United States last year was intended for people age 55 and older. It is still unclear when the new test will become available in Israel.
It is important to emphasize: This is not a screening test for the general population or for people without symptoms, and Alzheimer’s cannot be diagnosed on the basis of this result alone. It is intended for people age 40 and older who are undergoing evaluation because of cognitive decline. Doctors must interpret the result alongside a medical examination, the patient’s medical history and additional tests.
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The new blood test is designed to help diagnose Alzheimer’s in people age 40 and older with cognitive symptoms
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How the new blood test works
The PrecivityAD2 test was developed and evaluated by C2N Diagnostics, a company founded at Washington University in St. Louis. The test is based on technology developed by Dr. Randall J. Bateman and Dr. David M. Holtzman, neurology experts at the university and co-founders of the company. Their research on amyloid-beta protein in the brain and cerebrospinal fluid helped lay the groundwork for the development of blood tests for Alzheimer’s. Studies over the years have shown that the buildup of amyloid-beta deposits in the brain is associated with Alzheimer’s disease.
Dr. Talya Nathan Photo: Omer HacohenThe test measures several proteins linked to Alzheimer’s in a blood sample, including different forms of amyloid beta and tau protein. It uses an advanced technology known as high-resolution mass spectrometry. The data are then combined using an algorithm to produce a score from 0 to 100 that estimates the likelihood of amyloid deposits being present in the brain.
According to data released by C2N, the test was evaluated in a study involving 1,142 people with signs of cognitive decline. Among those who received a positive result, amyloid deposits were indeed found in the brain in 97.6% of cases. Among those who received a negative result, no deposits were found in 93.1% of cases. The results were compared with amyloid PET scans or biomarker testing of cerebrospinal fluid.
A result classified as “likely positive” was reported in 17.3% of participants, and amyloid deposits were found in 77.3% of those cases.
According to the company, the test was able to detect amyloid deposits both in people with mild symptoms and in those with more advanced cognitive decline. Its accuracy was maintained in older age groups and among people with common underlying conditions, including cardiovascular disease, kidney disease, diabetes, depression, obesity and autoimmune or inflammatory diseases.
“The PrecivityAD2 test provides an accurate and reliable way to detect the presence of brain amyloid plaques associated with Alzheimer’s disease pathology based on a single blood draw,” Bateman said in a statement published by Washington University.
He added that FDA approval would allow the test to reach more patients and help provide earlier and more accurate diagnosis for people seeking evaluation of symptoms such as memory loss.
Toward earlier and more accessible diagnosis
Early diagnosis is especially important today, now that the first treatments capable of slowing the progression of Alzheimer’s have become available. These treatments are more effective when started at an early stage, and additional experimental drugs are under development.
The blood test could offer a more accessible and less invasive option than cerebrospinal fluid testing and help doctors determine whether additional tests, such as a PET scan, are needed. However, it does not replace a full medical evaluation.
Early diagnosis may allow patients to begin treatment when it is more effective
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According to The Clinical Trial Vanguard, lowering the age threshold could also affect Alzheimer’s research. Today, 83% of active trials in the field already use biomarkers. Blood tests could allow researchers to screen larger numbers of trial candidates more simply and cheaply than with PET scans or lumbar punctures.
The publication also noted that Alzheimer’s-related changes in the brain can begin accumulating 15 to 20 years before symptoms appear. As a result, in a 40-year-old beginning to experience memory or thinking problems, amyloid deposits may have started building up in the brain as early as the person’s mid-20s.
In May last year, the FDA approved Fujirebio’s Lumipulse G pTau217/β-Amyloid 1-42 Plasma Ratio blood test for people age 55 and older. Another test was approved last year to help primary care physicians rule out Alzheimer’s disease. PrecivityAD2 is the third blood test of its kind to be approved in about 15 months, and the first intended for people as young as 40.
According to C2N, between 19 million and 20 million Americans age 65 and older are living with cognitive impairment. Hundreds of thousands more people between ages 45 and 65 may also benefit from earlier diagnosis.
The test is already available in the United States in a laboratory-developed version that has been validated under U.S. clinical laboratory standards. The FDA-approved version is expected to become available later this year and may be ordered by health professionals experienced in diagnosing cognitive decline.
Washington University said the approval could also help pave the way for insurance coverage, making the test less expensive and more accessible.