Blood tests designed to detect Alzheimer’s disease are being marketed as quick and convenient tools for diagnosing memory problems. But new research from Rutgers Health warns that these tests may be less accurate for certain groups—especially Black patients—and should be interpreted with caution.
The study, published in Alzheimer’s & Dementia, was led by Dr. William Hu, director of the Rutgers Center for Healthy Aging Research and chief of cognitive neurology at Rutgers.
According to Hu, these blood tests are increasingly being offered to primary care doctors and directly to older adults who are concerned about cognitive decline. However, the research team found major racial disparities in test accuracy, which could lead to missed or incorrect diagnoses.
“These tests may offer some value to doctors who understand their limits,” said Hu, “but there’s no reason for patients to spend $1,200 to $2,000 on them out-of-pocket. They’re rarely covered by insurance and can be misleading.”
The research focused on p-Tau217, a key Alzheimer’s biomarker that has been validated in spinal fluid, where it is more concentrated. But the new generation of tests attempts to measure these proteins in blood, where levels are much lower—and more affected by other health conditions.
This is especially problematic for Black patients, who naturally have lower p-Tau217 levels in spinal fluid to begin with. When these lower levels are mirrored in blood, it can make the disease even harder to detect.
To better understand these effects, the team studied 221 participants—Black, white, and ethnic Chinese—who underwent brain imaging, clinical evaluations, and had blood and spinal fluid samples taken on the same day. The results showed a 70% correlation between p-Tau217 levels in spinal fluid and blood. But this correlation didn’t tell the whole story.
The test worked much better in white participants, with:
- 90.3% sensitivity (ability to detect those with the disease)
- 81.1% specificity (ability to rule out those without it)
- 87% positive predictive value (likelihood that a positive result means the person actually has Alzheimer’s)
In contrast, for Black participants, performance dropped:
- 73.7% sensitivity
- 72.5% specificity
- 58% positive predictive value
This means that not only are Black patients more likely to be missed by the test when they actually have Alzheimer’s, they’re also more likely to get false positives—a troubling outcome for a serious diagnosis.
The differences in test accuracy could not be fully explained by previously known disparities in spinal fluid biomarkers, suggesting that the blood tests themselves may introduce new layers of inaccuracy.
Interestingly, among Chinese participants in the study, the test performed similarly to white participants, indicating that race-specific biological differences—rather than socioeconomic factors alone—may influence how well these blood tests work.
Hu compared the current stage of Alzheimer’s blood tests to early home COVID tests, which were not always reliable but improved over time. “In five to 10 years, these tests may become much more dependable,” he said, “but right now, they’re not ready to replace a proper neurological evaluation.”
The researchers urge anyone concerned about memory loss to see a neurologist rather than relying on blood test results alone. Early detection is vital—especially because new Alzheimer’s treatments work best in the early stages of the disease. Yet, about half of all Alzheimer’s cases in the U.S. go undiagnosed, often until symptoms are advanced.
In conclusion, while blood tests for Alzheimer’s show promise, this study makes it clear they still have serious limitations, particularly for Black patients. More work is needed to refine these tools and ensure they are equally accurate for all populations before they can be used as reliable, standalone diagnostic options.
If you care about Alzheimer’s, please read studies about the likely cause of Alzheimer’s disease, and new non-drug treatment that could help prevent Alzheimer’s.
For more information about brain health, please see recent studies about diet that may help prevent Alzheimer’s, and results showing some dementia cases could be prevented by changing these 12 things.
The research findings can be found in Alzheimer’s & Dementia.
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