New Blood Tests Show Promise for Early Alzheimer’s Detection

Recent research highlights the potential of blood tests to detect biomarkers associated with Alzheimer’s disease, suggesting a significant step toward early diagnosis. While scientists strive to develop simple blood tests that can serve as an early warning system, new findings indicate that tracking changes in specific protein biomarkers over time may yield more reliable results than relying on a single test.

A study presented in March 2023 revealed that conditions like obesity can obscure signals of Alzheimer’s by diluting proteins linked to the disease. This dilution can make a solitary blood test less dependable. Additionally, another study found that individuals who expressed concern about their memory but performed normally on cognitive assessments exhibited a notable increase in Alzheimer’s biomarkers in their blood over a five-year period, particularly those with early Alzheimer’s indicators in their spinal fluid. The findings underscore the importance of monitoring biomarker changes over time as opposed to relying solely on initial test results.

Advancements in Detection Technologies

Historically, diagnosing Alzheimer’s involved brain scans or spinal taps. Physicians utilize PET scans, where a radioactive tracer highlights amyloid protein clusters in the brain, believed to be contributors to cognitive decline. Abnormal amyloid accumulation can lead to the alteration of tau protein, which disrupts neuronal communication and results in memory loss. However, these methods are typically performed only in later stages of cognitive decline due to their high costs, limited availability, and insurance challenges.

The rise in Alzheimer’s cases has intensified the urgency for innovative diagnostic methods. In recent years, blood biomarker testing has gained traction, with the U.S. Food and Drug Administration (FDA) approving two blood tests that identify Alzheimer’s-related biomarkers. The Alzheimer’s Association has also released its first clinical guidelines for using these tests in specialty care settings.

According to Sheena Aurora, a practicing neurologist and vice president of medical affairs at the Alzheimer’s Association, the two approved tests serve distinct purposes. One is a “rule-out” test designed to help primary care providers determine if amyloid buildup is unlikely contributing to symptoms. The other is a “rule-in” test for specialists, indicating a higher likelihood of Alzheimer’s-related proteins in the brain.

“The tests are a tool,” Aurora stated, emphasizing their use alongside other diagnostic measures such as family history and cognitive assessments. She cautioned that these tests are not intended for general screening but should be administered by clinicians experienced in dementia care.

Challenges and Limitations of Blood Tests

While blood tests hold promise, researchers stress caution due to factors that may compromise their accuracy. Chronic conditions, particularly kidney function, can significantly impact blood test results. A study led by Corey Bolton, a clinical neuropsychologist at Vanderbilt University Medical Center, revealed that approximately one-third of older adults with kidney issues may receive unreliable results. The effects were most pronounced for the neurofilament light chain biomarker, which indicates nerve damage in the brain.

Bolton remarked that “this biomarker was no longer useful for individuals with stage three kidney disease.” The findings highlight the broader challenge of interpreting blood tests for Alzheimer’s, as conditions like obesity and vascular diseases can alter protein levels, complicating the diagnostic process.

The Centers for Disease Control and Prevention (CDC) estimates that about 34% of Americans over age 65 have chronic kidney disease, a reality that disproportionately impacts certain communities. Understanding how these chronic conditions affect blood test reliability is crucial for future research.

The need for personalized approaches to Alzheimer’s detection and treatment is becoming increasingly evident. Argonde C. van Harten, a neurologist at the Alzheimer Center Amsterdam, emphasized the importance of tailoring diagnostic methods to individual patients, stating, “In the future, we’ll need personalized treatment early in the disease.”

The study conducted by Harten and colleague Calvin Trieu followed 298 participants who reported memory concerns yet performed normally on cognitive tests over five years. Researchers measured Alzheimer’s-linked proteins every two years and found that a greater increase in these proteins correlated with measurable declines in cognitive function. The study determined that about 20% of participants who initially exhibited normal biomarker levels later developed abnormal ones.

Harten noted that their findings are group-level results and should not be used to predict outcomes for individuals. She acknowledged the limitations of their cohort, which was predominantly young and healthy, with few chronic conditions.

Taking multiple blood tests over time can provide a more comprehensive understanding of a patient’s cognitive health. Cyrus A. Raji, a neuroradiologist at Washington University, studied 407 individuals using leading commercial blood tests for Alzheimer’s biomarkers. Initial findings suggested that a higher body mass index was linked to lower Alzheimer’s signals on both blood and brain scans. However, over time, participants with obesity exhibited a notable increase in Alzheimer’s biomarkers compared to non-obese peers.

Raji explained that individuals with higher body mass indices dilute their biomarker values, making single time-point assessments misleading. “If you’re looking at just one time point, you’ll get fooled,” he stated.

The potential of blood-based tests to detect Alzheimer’s disease earlier than ever before offers hope for expanding access to millions who may be affected. As research continues, the emphasis remains on understanding the complexities of biomarker changes over time and the implications of chronic health conditions, ultimately paving the way for more effective early interventions.