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A timely and accurate diagnosis is crucial for determining the best treatment options for people living with Alzheimer’s disease or a related dementia. In the past, the only sure way to know whether a person had a specific type of dementia was through autopsy. Today, NIH-funded biomarker research has led to more reliable, more affordable, and less invasive tests that help diagnose and differentiate among the types of dementia.
First blood test for a biomarker of Alzheimer’s now validated in clinical trials
NIA’s small business research program funding supported the initial development of the PrecivityAD™ blood test , the first blood test for biomarkers of Alzheimer’s to become more broadly available to some doctors, dependent on state-specific availability reflecting U.S. Food and Drug Administration (FDA) guidelines. The test, developed by C2N Diagnostics, can help physicians evaluate patients who have cognitive impairment. C2N’s laboratory measures the concentrations of two forms of the amyloid protein: amyloids 42 and 40. The test also checks for the presence of a protein called apolipoprotein E. C2N uses these measures to calculate an Amyloid Probability Score, which can be used to estimate the likelihood of amyloid plaques in the brain.
In 2022, C2N Diagnostics published new findings from two independent studies that compared results from the PrecivityAD™ blood test with results from imaging tests in a total of 686 participants. The studies showed that the PrecivityAD™ blood test is 81% accurate in predicting the presence of amyloid plaques in the brain . These results reaffirm the test as an important tool to help diagnose Alzheimer’s.
New blood-based biomarker tests help clinicians more easily and accurately diagnose dementia
Some proteins from the brain can be measured by sensitive blood tests. The levels of certain proteins in the blood can change when someone has Alzheimer’s or a related dementia, and researchers are developing new methods to detect these changes. In the past year, NIH-funded science has led to these discoveries:
- A new blood test can accurately predict the presence of beta-amyloid plaques in the brain . This test could help lower the cost of accurately diagnosing Alzheimer’s or another dementia and expand availability of accurate, sensitive tests for dementia to more people.
- Two forms of the tau protein, called ptau217 and ptau181, have been found to be accurate blood-based biomarkers for Alzheimer’s . Additionally, evidence suggests ptau217 may be an especially accurate indicator of Alzheimer’s in diverse populations .
- The level of a protein called neurofilament light chain (NfL) in the blood can predict remaining lifespan in late life more accurately than currently used estimates based on physical and cognitive function.
Advances in brain imaging technology are improving dementia diagnosis
Brain imaging, also known as brain scans, can help detect changes in the brain that are linked to dementias. Advanced brain imaging techniques can identify tau tangles and beta-amyloid plaques, which are hallmarks of Alzheimer’s disease, and can help rule out other causes of cognitive impairment, such as a brain tumor. Recent NIH-funded discoveries in brain imaging technology for dementias include the following:
- In people living with Alzheimer’s, a small area of the brain called the locus coeruleus might show signs of the disease before any other brain area . The locus coeruleus communicates with other areas of the brain, affecting many functions including memory, wakefulness and attention, and response to stress. Changes in this region could serve as a biomarker for early diagnosis of the disease.
- A new tracer designed to detect living synapses (connections between nerve cells) that can be used together with brain imaging technology can help researchers study the connections between nerve cells in the brain . This new technique will help clarify how interrupted connections between nerve cells contribute to dementia diseases.
Biomarkers for dementia-related vascular damage gain momentum
Scientists are uncovering considerable knowledge about vascular contributions to cognitive impairment and dementia (VCID). Damage to the brain’s vascular system — the collection of arteries and blood vessels that supply oxygen and other nutrients to the brain — often occurs early and contributes to the severity of Alzheimer’s and other dementias. To help improve VCID detection, the National Institute of Neurological Disorders and Stroke (NINDS) and NIA fund and help lead the Biomarkers for Vascular Contributions to Cognitive Impairment and Dementia ( MarkVCID) consortium with the goal of identifying biomarkers that indicate problems with blood vessels in the brain.
In 2021, MarkVCID scientists published promising results from several candidate cerebrospinal fluid- and blood-based biomarkers as well as imaging-based biomarkers of VCID. The researchers also developed standardized, well-documented procedures to help with the large-scale rigorous validation of these candidate biomarkers. They are now testing the most promising biomarkers in larger-scale clinical trials in diverse populations.
Breakthrough test can help diagnose multiple types of dementia
Thanks in part to NIA funding, Amprion®, a biotechnology company, launched the SYNTap™ Biomarker Test . The test, which was granted FDA breakthrough device designation in 2022, detects abnormal forms of the protein alpha-synuclein in cerebrospinal fluid samples. Alpha-synuclein is misfolded in Lewy body dementia, but its presence is typically not confirmed until autopsy. Once approved by the FDA, the test will aid early diagnosis of these diseases and help detect the co-occurrence of Lewy bodies in people with Alzheimer’s, in whom it is thought to accelerate disease progression. Amprion is currently seeking FDA approval for the biomarker test.
Digital cognitive biomarkers can help predict cognitive decline
NIH supports research to develop minimally invasive strategies that help detect pre-symptomatic or early-stage Alzheimer’s. For example, digital cognitive biomarkers assess how well a person completes learning- and memory-related tasks on a digital device. Funded in part by NIA, newly developed and validated digital cognitive biomarkers for Alzheimer’s can help predict which seemingly healthy people may experience cognitive decline in the future.
Scientists identifying biomarkers for Alzheimer’s in people with Down syndrome
People who have Down syndrome have a high risk of developing Alzheimer’s: Almost all adults with Down syndrome have Alzheimer’s-related brain changes by age 40. NIA funds and helps guide the Alzheimer’s Biomarkers Consortium — Down Syndrome (ABC–DS), through which researchers identify early biomarkers of Alzheimer’s in adults with Down syndrome. ABC-DS is a longitudinal study that is funded in collaboration with the Eunice Kennedy Shriver National Institute of Child Health and Human Development and the NIH INCLUDE (Investigation of Co-occurring conditions across the Lifespan to Understand Down syndromE) project .
In 2021, based in part on ABC-DS data, researchers discovered that people who have Down syndrome have a profile of biomarkers very similar to people with a gene variant that causes an inherited form of Alzheimer’s. Results from this project will help doctors and scientists better understand the onset and progression of Alzheimer’s in people who have Down syndrome and will aid in therapy development.