Blood test for Alzheimer’s disease quite accurate, study shows

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In a new study from Washington University in St. Louis, researchers found a blood test is highly accurate in detecting early signs of Alzheimer’s disease.

They found that the blood test provides a robust measure for detecting amyloid plaques associated with Alzheimer’s disease, even among patients not yet experiencing cognitive declines.

Developed by the team, the blood test assesses whether amyloid plaques have begun accumulating in the brain based on the ratio of the levels of the amyloid-beta proteins Aβ42 and Aβ40 in the blood.

Researchers have long pursued a low-cost, easily accessible blood test for Alzheimer’s as an alternative to the expensive brain scans and invasive spinal taps now used to assess the presence and progression of the disease within the brain.

Evaluating the disease using PET brain scans—still the gold standard—requires a radioactive brain scan, at an average cost of $5,000 to $8,000 per scan.

Another common test, which analyzes levels of amyloid-beta and tau protein in cerebrospinal fluid, costs about $1,000 but requires a spinal tap process that some patients may be unwilling to endure.

In the study, the team estimated that prescreening with a $500 blood test could reduce by half both the cost and the time it takes to enroll patients in clinical trials that use PET scans.

Screening with blood tests alone could be completed in less than six months and cut costs by tenfold or more.

A commercial test based on Bateman’s research was certified in 2020 under the Clinical Laboratory Improvement Amendments (CLIA) program approved by FDA.

CLIA certification makes the test available for doctors in the United States.

A similar certification makes the test available in Europe. The test is not yet covered by most health insurance.

The current study shows that the blood test remains highly accurate, even when performed in different labs following different protocols, and in different cohorts across three continents.

To confirm the test’s accuracy, researchers applied it to blood samples from nearly 500 individuals enrolled in ongoing Alzheimer’s studies in the United States, Australia and Sweden.

The findings confirmed that the Aβ42/Aβ40 blood test provides highly accurate and consistent results for both cognitively impaired and unimpaired individuals across all three studies.

When blood amyloid levels were combined with another major Alzheimer’s risk factor—the presence of the genetic variant APOE4—the accuracy of the blood test was 88% when compared to brain imaging and 93% when compared to the spinal tap.

If you care about Alzheimer’s risk, please read studies about small changes in movement that may predict Alzheimer’s disease, and findings that deaths from Alzheimer’s far more common in these places in U.S.

For more information about brain health, please see recent studies about two common habits that can make your brain age fast, and results showing that COVID-related brain damage more likely in these people.

The study is published in Neurology and was conducted by Randall J. Bateman et al.

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