Simple Blood Tests to Detect Alzheimer’s Risk: Pros and Cons

New blood tests to detect early signs of Alzheimer’s are becoming available; but does a positive result mean you actually have the disease?

RESTOCK images/Shutterstock

Alzheimer’s disease is a looming threat as we age. The most common cause of dementia, Alzheimer’s afflicts roughly 1 in 9 people over 65—with women making up two-thirds of cases.

For years, Alzheimer’s could be definitively diagnosed only after death through autopsy. But promising new blood tests offer hope that doctors can determine who is most at risk and gain time to use new treatments that could slow the disease’s progression. However, these tests aren’t yet approved by the U.S. Food and Drug Administration (FDA) and don’t actually diagnose the disease; they only estimate risk.

Alzheimer’s Blood Tests Are Less Invasive

PET scans and cerebrospinal fluid-based tests are currently the standard for diagnosing Alzheimer’s, but they’re expensive. The average cost of a PET scan in the United States is about $6,000, and a spinal tap procedure is about $1,000.

But many doctors expect that less invasive, cheaper tests may soon be available.

Story continues below advertisement

Blood-based biomarker testing is a promising alternative, Dr. Anita Szerszen, director of inpatient geriatrics at Northwell Staten Island University Hospital in New York, told The Epoch Times.

“The specific group of blood biomarkers called phosphorylated tau proteins are so far the best possible candidates for identifying early changes in the brain that predict Alzheimer’s before symptoms such as memory loss emerge,” she said.

Also, two key developments may increase medicine’s focus on blood-based testing.

The FDA recently approved Biogen’s Aduhelm and Eisai’s Leqembi, both drugs designed to slow Alzheimer’s progression. Aduhelm’s approval has been mired in controversy, and some countries, including Canada, have refused to authorize the drug because of a lack of data supporting its efficacy.

Story continues below advertisement

Blood-based tests may be beneficial because doctors will have a quicker and less expensive way to tell who should be prescribed these medications without scheduling PET scans and spinal taps for all suspected cases.

Blood Tests Already Available 

Several blood tests exist for early Alzheimer’s detection, with varying accuracy based on test type and measured biomarkers. Although Dr. Szerszen said she wouldn’t recommend testing without discussing the implications and their interpretation with a specialist, researchers have generally found them effective at identifying early disease indicators. Available tests include the following:

• Protein test: The neurofilament light chain (NfL) test measures NfL protein levels, a neurodegenerative disease biomarker. Elevated levels of NfL have been found to correspond with the onset and progression of neurological diseases, including Alzheimer’s. However, the test isn’t specific to Alzheimer’s, and NfL protein is only considered evidence of neurodegenerative disease in general.
• Genetic test: The ApoE gene test looks for specific variants of a gene called ApoE that are associated with an increased risk of developing Alzheimer’s disease. The ApoE gene test reveals lifetime Alzheimer’s risk but can’t predict the disease.
• Plasma ratio test: In a recent study published in Neurology, one blood test detecting amyloid plaque buildup in the brain by measuring proteins in blood was nearly 90 percent accurate at predicting Alzheimer’s onset within four years. The commercial version of this test is called PrecivityAD.

The 1st Alzheimer’s Blood Test for Sale Direct-to-Consumer

Quest Diagnostics recently announced the first direct-to-consumer Alzheimer’s risk test: AD-Detect. It’s based on the same technology as the plasma ratio test.

“Blood tests like AD-Detect hold incredible potential to make Alzheimer’s disease risk assessment both accessible and convenient,” Dr. Michael K. Racke, medical director of Neurology at Quest Diagnostics, said in a press statement.

However, significant obstacles remain. AD-Detect doesn’t diagnose Alzheimer’s; it only estimates risk.

The Alzheimer’s Association says biomarker tests should currently be used to diagnose symptomatic patients, with results confirmed via spinal fluid tests or PET scans when possible.

Story continues below advertisement

No Alzheimer’s blood test has FDA approval yet. Although convenient access helps early detection efforts, concerns persist around invalidated tests lacking oversight.

Pros, Cons of Blood Testing for Alzheimer’s

The blood tests raise troubling questions. What if you test positive before symptoms arise? Would you take medications with serious side effects to slow the progression of an incurable illness? Would you want to know you may one day lose your identity to Alzheimer’s?

But Dr. Szerszen noted benefits, too. Those at risk may be motivated to improve lifestyle factors, control diabetes, lower blood pressure, or treat hearing loss to alter the Alzheimer’s trajectory.

“Knowing the risk gives also a person a chance to plan for the future, take care of their legal and financial issues, set advance care directives, or even retire earlier,” she said.