New Research Highlights Promise of Blood Tests for Alzheimer’s Detection

Recent studies reveal significant advancements in blood tests designed to detect biomarkers for Alzheimer’s disease, paving the way for earlier diagnosis. Research indicates that monitoring changes in specific protein biomarkers over time offers a more accurate assessment than relying on a single test result.

One study presented at the Radiological Society of North America’s annual meeting highlights how obesity can obscure vital signals of Alzheimer’s by diluting proteins associated with the disease. This dilution can lead to less reliable outcomes from individual blood tests. Another study suggests that individuals who express concern about their memory but perform well on cognitive tests—yet show signs of early Alzheimer’s in their spinal fluid—exhibit a more pronounced increase in relevant proteins over five years compared to those without spinal fluid evidence.

Cyrus A. Raji, a neuroradiologist and principal investigator at the Mallinckrodt Institute of Radiology at Washington University School of Medicine, emphasized the revolutionary nature of these findings, noting, “Twenty years ago, we could only diagnose Alzheimer’s at autopsy. This has revolutionized the field.”

Advancements in Early Detection

Traditionally, diagnosing Alzheimer’s relied heavily on brain scans or spinal taps. During a positron emission tomography (PET) scan, a radioactive tracer helps visualize amyloid protein clumps in the brain, which are linked to cognitive decline. Abnormal amyloid accumulation can lead to changes in another protein, tau, ultimately disrupting neuronal communication and prompting memory loss. Spinal taps measure these proteins in the cerebrospinal fluid. Unfortunately, many patients do not undergo these tests until they are in the later stages of cognitive decline, often due to high costs, limited availability, and insurance obstacles.

With rising numbers of diagnosed cases, researchers are eager to enhance detection methods. In the past three to five years, the development of blood biomarker tests has accelerated significantly. The FDA has recently approved two such tests for Alzheimer’s-related biomarkers, and the Alzheimer’s Association has issued its first clinical guidelines for their implementation in specialized care settings.

According to Sheena Aurora, a neurologist and vice president of medical affairs at the Alzheimer’s Association, the FDA-approved tests serve different purposes. One functions as a “rule-out” test to help primary care providers determine if amyloid build-up is unlikely to be contributing to symptoms, while the other acts as a “rule-in” test for specialists, indicating a higher likelihood of Alzheimer’s-linked proteins in the brain.

“The tests are a tool,” Aurora stated. “They should be used in conjunction with other diagnostic measures—not in isolation.” She cautioned against individuals pursuing these tests independently, noting their limited coverage under Medicare.

Challenges with Blood Tests

Despite the promise of blood-based tests, researchers urge caution due to various factors that can affect the reliability of results. For instance, kidney function plays a significant role, as studies indicate that about one-third of older adults with kidney conditions may receive unreliable results. Corey Bolton, a clinical neuropsychologist and assistant professor at Vanderbilt University Medical Center, found that mild kidney dysfunction can alter several Alzheimer’s-related biomarkers, particularly neurofilament light chain, a common indicator of nerve damage in the brain.

“Biomarkers were no longer useful for individuals with stage three kidney disease,” Bolton explained. With nearly 34% of Americans over the age of 65 estimated to have chronic kidney disease, understanding how this condition impacts test accuracy is crucial.

As researchers continue to investigate these challenges, they seek to create workarounds, such as comparing ratios of proteins. However, most biomarker validation studies have predominantly involved homogeneous groups, raising concerns about the applicability of findings across diverse populations.

Argonde C. van Harten, a neurologist at Amsterdam UMC, noted the necessity for personalized treatment strategies as research progresses. “In the future, we’ll need personalized treatment early in the disease,” she stated. Blood-based biomarkers might provide a minimally invasive approach to understanding biological changes associated with Alzheimer’s.

The importance of tracking biomarker changes over time emerged clearly in a study involving 298 participants who expressed memory concerns but scored well on cognitive tests. The research measured Alzheimer’s-linked proteins in blood every two years and conducted annual cognitive assessments. Approximately 20% of participants who initially exhibited normal biomarker levels later developed abnormal ones.

Harten emphasized that the study’s findings should not be interpreted as predictive for individuals, as the cohort comprised younger adults with fewer chronic conditions.

Tracking multiple blood tests over time yields a comprehensive view of cognitive health, contrasting sharply with the limitations of a single test. Raji’s investigation of 407 individuals using six leading commercial blood tests found that higher body mass index (BMI) correlated with lower initial Alzheimer’s signals. Over time, however, participants with obesity showed significant increases in Alzheimer’s-linked proteins compared to their non-obese counterparts.

“Larger bodies have a higher BMI, which dilutes the values,” Raji explained. “Looking at just one time point can be misleading.”

As research continues to evolve, the potential for blood tests to serve as effective early detection tools for Alzheimer’s remains promising, offering hope for millions affected by the disease.