Monday, June 23, 2025

New! Blood Test for Confirming Alzheimer's Disease

 


How Alzheimer’s Has Historically Been Diagnosed

In the United States, the incidence of Alzheimer's Disease among older adults is 10% and increases with age. However, that means that the overwhelming majority, or 90%, do NOT have it. Every lost key doesn't mean Alzheimer's Disease. As a gerontologist, I have found that older people are hyper-aware of memory loss and many are downright terrified of it. 

Historically, diagnosis has been limited. Magnetic resonance imaging (MRI) scans can show structural degeneration, brain cell activity changes and/or biological deviations, but often can’t confirm if these changes are caused by Alzheimer’s, another condition, or aging. 

Cerebral spinal fluid (CSF) tests, which involve an invasive low back puncture, can identify Alzheimer's biomarkers, but the levels, even in the same sample, often vary significantly from institution to institution and across different testing platforms. 

Positron emission tomography (PET) scans that specialize in visualizing amyloid plaques and tau protein tangles -- hallmark signs of Alzheimer’s – can be accurate, but technically challenging to perform and require strict quality control. Often, physicians are hesitant to order scans and instead, rely on neuropsychological evaluations, which do not provide a definitive diagnosis. Moreover, imaging tests are costly, time-consuming, and expose patients to radiation. Some clinicians don’t consider their results definitive and prefer to order these PET scans as secondary tests to confirm an Alzheimer’s diagnosis.   

Neurologists typically use the NIA-AA Core Clinical Criteria for Alzheimer's  Disease developed by McKhann et al. in 2011. According to leading Neurologist Dr. David Wolk, a clinical diagnosis is far from perfect, around 75% accurate. It includes evaluation of the patient's overall cognitive functioning, behavioral changes, other accompanying clinical features, imaging, lab tests, and informant reports from primary caregivers. 

New Blood Tests

Laboratories are working on blood tests that can consistently measure changes in Alzheimer’s biomarkers before and after symptoms begin appearing. A couple of years ago, the University of Washington developed a laboratory test, called soluble oligomer binding assay (or SOBA), to measure beta-amyloid oligomers in the blood, an early sign of Alzheimer’s disease that is thought to trigger and progress the disease, according to a study published in the Proceedings of the National Academy of Sciences.  

More recently, the US Federal and Drug Administration (FDA) approved the first blood test for Alzheimer's disease. Fujirebio Diagnostics, a biotechnology company, created a test –the Lumipulse G pTau217/ß-Amyloid 1-42 Plasma Ratio. It measures the levels of and ratio between beta-amyloid 1-42 and pTau217 in plasma. The presence of these proteins in plasma suggests amyloid plaques in the brain.  

The Lumipulse G pTau217/ß-Amyloid 1-42 Plasma Ratio multi-center clinical study included nearly 500 individual plasma samples from adult participants who demonstrated cognitive impairment. Samples were tested using Lumipulse G pTau217/ß-Amyloid 1-42 Plasma Ratio and compared with amyloid PET scan or CSF test results. The FDA evaluated the results and findings showed:

  • Almost 92 percent of people with positive results had the presence of amyloid plaques confirmed by a PET scan or CSF test result.
  • 97 percent of people with negative results. The absence of amyloid plaques was confirmed by a PET scan or CSF test result.  
  • Less than 20 percent of people in the study had an undetermined result.

The FDA concluded that this new test is reliable, minimally invasive, easier to perform, and more accessible than other Alzheimer’s tests. Since it’s a blood draw, the only risk associated with the test is a possible false positive or false negative result. This is problematic as it contributes to a misdiagnosis. However, results should be interpreted in combination with other patient clinical information. The test is meant to be used by a specialist in patients with signs and symptoms of cognitive decline. The blood test is NOT designed for or intended to be a screening. Also, the research sample of 500 participants suggests further studies with larger participant pools are required. 

Although there is no known cause, research suggests that Alzheimer’s may be triggered by a combination of risk factors including age, genetics (early onset only), head injuries, an unhealthy lifestyle, heart disease, and environmental exposures. Currently, there is no proven method of prevention, but you can help lower your risk of dementia by living a brain-healthy lifestyle and minimizing risks. It is never too late to start! AgeDoc

Resources:

White, J.V.. May 2025. Harvard University Medical School, Comprehensive Dementia Update. Cambridge, MA. 

Tiberian, Janet. MD-VIP Newsletter dated 6/22/25. 

 

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