Alzheimer’s blood tests more likely to misdiagnose Black patients, study finds
Several blood tests used to diagnose Alzheimer’s disease are less accurate for African Americans than white patients, according to research from Washington University.
The gold standard for Alzheimer’s diagnosis typically involves brain imaging and spinal fluid testing, but in recent years, biotech companies have developed an array of cheaper, less invasive blood tests to detect early signs of the disease.
The tests measure concentrations of specific proteins that form sticky plaques and tangles in the brain, causing the memory-robbing disease. But when Washington University researchers tested the accuracy of leading Alzheimer’s blood tests, they found three out of four performed differently depending on the patient’s race. Black patients were more likely to be misdiagnosed with Alzheimer’s disease, putting them at risk of receiving the wrong medical treatment.
More than 6 million people in the U.S. had Alzheimer’s disease in 2021, based on federal data from the Centers for Disease Control and Prevention. Black patients are about twice as likely to develop the disease and other related forms of dementia and often have more severe symptoms.
But nearly all of the research and clinical testing used to develop Alzheimer’s blood tests has involved white patients, said Rebecca Edelmayer, who leads scientific engagement for the Alzheimer’s Association and was not involved in the study.
“We need to be able to understand what these technologies are telling us across different races and ethnicities and people from all socioeconomic and cultural backgrounds to make sure that the diagnoses are actually predictive of the type of disease they have in their brain,” Edelmayer said.
By some estimates, Black patients make up just 5% of clinical trial participants nationally. At the Knight Alzheimer Disease Research Center at Washington University, white research participants outnumber Black patients 8-1.
To test the accuracy of four leading Alzheimer’s blood tests, Washington University researchers matched 76 pairs of Black and white participants based on age, gender and cognitive status. After testing each patient’s blood for common proteins associated with Alzheimer’s disease, the team used a combination of brain scans and spinal fluid tests to confirm the diagnosis.
Only one of the tests, known as PrecivityAD, accurately diagnosed patients regardless of their race. The three others were more likely to misdiagnose Black patients with Alzheimer’s disease.
That’s cause for concern, said Dr. Suzanne Schindler, a neurologist at Washington University who specializes in Alzheimer’s and dementia.
“If these tests are not working accurately in all groups, that means you will be disproportionately misdiagnosing one group, which is obviously a bad thing,” said Schindler, who co-authored the study. “But within a few years, what it could mean is that you’re treating people with the wrong medications, and that's even more concerning.”
Black patients in the study were more likely to have diabetes and high blood pressure, which can affect the accuracy of Alzheimer’s blood tests.
Though the blood tests are not yet widely used to diagnose Alzheimer’s, that could change as new drug treatments hit the market. The U.S. Food and Drug Administration approved Aduhelm as an Alzheimer’s treatment last June. But insurers were reluctant to pay for the drug, largely due to its high cost and unproven benefits, and last week drugmaker Biogen stopped marketing it.
Other drugs are already in the development pipeline, Schindler said, which could boost demand for blood tests.
“There are a number of other drugs for Alzheimer's disease that are in late stages of clinical trials,” she said. “If they’re approved, we’re going to be doing a lot more testing for Alzheimer's disease, because all of these treatments will require these tests before you get the drug.”
The goal, she said, is to ensure Alzheimer’s tests work well for all patients — before demand spikes.
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