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.
