USC Researchers Identify New Brain Imaging Benchmark for Alzheimer’s Detection Across Diverse Populations

A research team from the Keck School of Medicine at USC’s Mark and Mary Stevens Neuroimaging and Informatics Institute (Stevens INI) has identified a promising new brain imaging marker that may improve how Alzheimer’s disease (AD)-related biological changes are classified especially among Hispanic and non-Hispanic White populations. The findings, published in Imaging Neuroscience, are part of the Health and Aging Brain Study–Health Disparities (HABS-HD), a collaborative, multi-university project led by the University of North Texas Health Science Center and supported by the National Institute on Aging.

Using tau PET scans, which visualize abnormal tau protein accumulations in the brain, the researchers analyzed data from over 675 older adults. Their goal was to determine an optimal tau signal or “cut-point” that could distinguish individuals showing clinically relevant signs of AD from those aging normally.

Tau PET involves a small dose of a radioactive tracer that illuminates areas with tau buildup, a hallmark of Alzheimer’s. By measuring these levels, researchers aim to set reliable thresholds tau cut-points that signal early disease risk.

In this study, researchers compared tau PET scans from cognitively impaired and unimpaired participants, finding a tau cut-point that effectively identified cognitive impairment but only under certain conditions. It was accurate in individuals who also had amyloid buildup and who were either Hispanic or non-Hispanic White. The cut-point did not work as reliably in non-Hispanic Black participants.

“Our tau cut-point successfully identified cognitive impairment, but only when amyloid was also present and only in Hispanic and non-Hispanic White groups,” said senior author Meredith N. Braskie, PhD, assistant professor of neurology. “In non-Hispanic Black individuals, the results didn’t hold, suggesting other biological or social factors may be contributing to cognitive decline.”

To conduct the study, the team used an advanced tracer called 18F-PI-2620 to measure tau in the medial temporal lobe, a brain region linked closely with memory. High tau levels in this region were strongly associated with cognitive impairment.

“While our results support existing research linking tau in the medial temporal lobe to memory decline, setting a clear threshold using 18F-PI-2620 is a critical step toward clinical application,” said lead author Victoria R. Tennant, a PhD candidate in USC’s Neuroscience Graduate Program. “However, the lack of accuracy in non-Hispanic Black participants underscores the urgent need to include more diverse populations and examine both biological and social factors in Alzheimer’s research.”

These findings align with a growing emphasis on ensuring Alzheimer’s diagnostic tools are effective across all populations—not just those typically included in clinical trials. Alzheimer’s progression is known to follow a pattern: amyloid plaques build up early, while tau tangles correlate more directly with cognitive symptoms like memory loss.

“This kind of brain imaging is vital for identifying risk and understanding disease progression,” said Arthur W. Toga, PhD, director of Stevens INI. “This work adds to a rich body of data from HABS-HD, the most comprehensive study of Alzheimer’s and related dementias in diverse communities. From uncovering ethnic differences in biomarkers to evaluating social and vascular factors, HABS-HD is driving progress toward more personalized, equitable Alzheimer’s care.”

Source: https://keck.usc.edu/news/usc-researchers-define-brain-scan-marker-to-better-classify-alzheimers-disease-related-changes