Recent scientific research has led to a blood test that can predict Alzheimer's disease. However, a new study by Rutgers Health has raised significant concerns about the reliability of Alzheimer's disease blood tests, particularly for Black patients.
The research, led by William Hu, director of the Rutgers Center for Healthy Aging Research, calls for a cautious interpretation of these tests, which are currently marketed to primary care physicians and older adults worried about cognitive decline.
Hu said these tests may offer some value to primary care doctors who understand their limitations, but there is no reason for patients with memory concerns to purchase these tests, which are priced between $1,200 and $2,000 and are rarely covered by insurance.
The study found that concentrations of Alzheimer's biomarkers are notably lower in blood compared to spinal fluid, where they have been validated as diagnostic tools for White patients. This discrepancy is particularly pronounced in Black patients, who naturally have lower biomarker levels in their spinal fluid. Additionally, worse memory function can elevate blood biomarker levels, complicating the test's accuracy.
Mild conditions could go undiagnosed
Hu said the blood tests have many caveats, and that poor transfer of proteins from spinal fluid to blood means many patients will go undiagnosed, especially if their disease is mild, while the ability of other ailments to increase these proteins in the blood can lead to false positives.
The research involved participants from Rutgers and Emory University, including Black, non-Hispanic White, and ethnic Chinese individuals. All 221 participants underwent detailed clinical evaluations and brain imaging, with both blood and spinal fluid samples collected on the same day. Automated testing systems were used to measure levels of specific proteins, particularly p-Tau217.
The study revealed a 70% correlation between protein levels in spinal fluid and blood, with significant racial disparities. For White participants, the blood test showed 90.3% sensitivity and 81.1% specificity, whereas for Black participants, sensitivity dropped to 73.7% and specificity to 72.5%. The positive predictive value was much higher for white participants (87%) compared to Black participants (58%).
Hu noted that while the tests may eventually become reliable, they currently require significant refinement.
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