FDA Approves First Blood Test for Alzheimer’s Detection

The U.S. Food and Drug Administration (FDA) has recently authorized a blood test capable of identifying signs of Alzheimer’s disease in the brain, based on several studies. This test marks a significant development as the first blood test available for this prevalent form of dementia.

Here’s a look at how it functions and why it might be important for patients.

Why Introduce a Blood Test for Alzheimer’s?

Alzheimer’s disease is increasingly common, largely due to the growing number of older adults. By 2025, it’s estimated that around 7.2 million Americans aged 65 and older will be living with Alzheimer’s dementia. The risk escalates with age; while about 5% of individuals aged 65 to 74 have Alzheimer’s, over 33% of those 85 and older are affected.

Once a healthcare professional confirms cognitive decline, this new blood test can replace traditional diagnostic tests to assess whether the patient likely has Alzheimer’s. Previously, standard diagnostic methods, which include PET scans and lumbar punctures, could be invasive and costly. Physicians sometimes also utilize MRIs or CT scans to eliminate other potential causes of cognitive issues.

This novel test gauges the ratio of two proteins in the blood, providing insight into the presence or absence of amyloid plaques—key indicators of Alzheimer’s found in the brain.

For individuals facing memory issues, visiting a primary care physician (PCP) is essential, who can conduct cognitive evaluations. If signs of cognitive impairment emerge, then a referral to a neurologist for further assessment is the next step.

Both dementia specialists and PCPs can now order this blood test to aid in diagnosis, according to Dr. Gregg Day, a neurologist from the Mayo Clinic who led a study published in the Journal of the Alzheimer’s Association. A separate 2024 study in JAMA indicates that whether ordered by a PCP or specialist, the blood test is equally reliable for confirming suspected Alzheimer’s diagnoses.

With these test results, PCPs can determine the necessity to refer patients to specialists for potential treatments or manage prescriptions themselves, such as donepezil, known to improve cognitive functioning in Alzheimer’s patients. Following FDA clearance, it’s anticipated that Medicare and private insurers will begin covering this new blood test.

Who Should Consider the Blood Test?

The “Lumipulse G pTau217/ß-Amyloid 1-42 Plasma Ratio” test is aimed at individuals aged 55 and older who have confirmed symptoms of cognitive decline. Its purpose is to facilitate early detection of amyloid plaques linked to Alzheimer’s disease.

Dr. Sayad Ausim Azizi, a clinic chief at the Yale School of Medicine, emphasizes that early detection is crucial. He compares the Alzheimer’s brain to a rusty engine, whereby plaque buildup complicates functioning. While some FDA-approved treatments can help slow brain degeneration, they do not remove the plaque itself. Available therapies have shown the potential to decelerate cognitive decline by 30% to 40%, allowing patients to maintain functioning for a more extended period.

In practical terms, if someone is living independently now, neglecting treatment might reduce that capacity significantly in the years to come. On the flip side, starting treatment sooner could extend their independence for longer.

Can the Blood Test Serve General Screening Purposes?

This test isn’t meant for the general population but rather for individuals displaying signs of Alzheimer’s, as emphasized by Day and Azizi. It’s important as some amyloid presence in the brain is a normal part of aging, and a positive test result does not necessarily indicate future Alzheimer’s development.

Azizi raises a valid point: treatments for Alzheimer’s are not without risks. For instance, the medication lecanemab requires a bi-weekly infusion initially, with a transition to once every four weeks thereafter, both carrying potential side effects like headaches or nausea.

What About False Positives?

There’s a possibility of false positives with this new test, meaning someone might test positively without actually having Alzheimer’s. The amyloid markers it detects can also relate to other health issues. For example, Day notes that abnormal kidney function can lead to amyloid accumulation in the brain, thereby complicating diagnosis. Hence, a kidney function assessment is advisable alongside the Alzheimer’s test.

The Mayo Clinic study involved about 510 participants, of which 246 showed cognitive decline. It confirmed that 95% of those with cognitive symptoms had Alzheimer’s, yet 5.3% exhibited false negatives, while 17.6% resulted in false positives. Most of those with false positives had changes in their brains akin to Alzheimer’s, but their symptoms were attributed to other conditions, such as Lewy body dementia.

It’s noteworthy that the populations tested often skew healthier than average. Therefore, when expanded to a more diverse demographic, those with conditions like sleep apnea or kidney disease could also yield positive results despite not having Alzheimer’s.

Could This Blood Test Further Alzheimer’s Research?

According to Azizi, this blood test could significantly assist research by connecting clinical symptoms to blood test findings, marking progress in early diagnosis and treatment. It could also help track treatment effectiveness in patients using approved medications or participating in clinical trials. As research moves forward, assessing the efficacy of blood testing in broader, more diverse populations is also a priority.