South Middlesex Times

Research from Rutgers Health highlights the need for cautious interpretation of blood tests for Alzheimer's disease, especially concerning Black patients. William Hu, senior author of the paper published in Alzheimer’s and Dementia, warns against relying solely on these tests. "These tests are currently geared towards primary care physicians and directly to older adults concerned about cognitive performance," said Hu, who is also the director of the Rutgers Center for Healthy Aging Research and Chief of Cognitive Neurology & Alzheimer’s Disease Clinic. He noted that while they might provide some value to doctors aware of their limitations, patients should not purchase them as they are expensive and rarely covered by insurance.

The study found that concentrations of an Alzheimer’s biomarker are significantly lower in blood than in spinal fluid. This discrepancy is more pronounced in Black patients who naturally have lower levels of this biomarker in their spinal fluid. Memory function deterioration can also raise blood biomarker levels. Hu explained, “The blood tests have many caveats,” noting that poor protein transfer from spinal fluid to blood could lead to undiagnosed cases, particularly mild ones, while other ailments might cause false positives.

Test results from participants at Rutgers and Emory University were examined by researchers. The cohorts included Black and non-Hispanic white participants, with the Rutgers cohort also having ethnic Chinese participants. Hu stated, “For Black patients, it’s a double whammy," highlighting challenges in diagnosing Alzheimer's through both spinal fluid proteins and blood tests.

Participants underwent clinical evaluations and brain imaging; most provided both blood and spinal fluid samples on the same day. Automated testing systems measured specific proteins like p-Tau217 in these samples. A 70% correlation was found between protein levels in spinal fluid and blood across races but with significant disparities: a 90.3% sensitivity rate for white participants compared to 73.7% for Black participants when using a threshold optimized for detecting Alzheimer's.

The positive predictive value was notably higher among white participants (87%) than Black participants (58%). These disparities persisted despite accounting for known racial differences in protein levels within spinal fluid, suggesting additional issues introduced by the blood test itself.

In patients of Chinese ancestry, test performance aligned closely with that seen in white patients. Hu mentioned that while these tests may eventually become reliable tools after refinement over five to ten years, currently they resemble early home COVID-19 tests with accuracy issues.

Researchers urge those with memory concerns to consult neurologists rather than relying solely on these blood test results. They emphasized that approximately half of all Americans with Alzheimer’s remain undiagnosed—especially those at early stages where treatment could be most beneficial.