Does Race Affect Interpretation of Alzheimer’s Blood Test Results?

A new study from Washington University School of Medicine in St. Louis shows that race has an impact on the performance of three different experimental Alzheimer’s disease (AD) blood tests used to determine those who are in the early stages of the disease. The research, published in the journal Neurology on April 21, showed that these three blood tests provided different results depending on if patients were Black or White.

However, the research showed that a fourth test was just as effective at revealing those in the early stages of Alzheimer’s regardless of race, though it’s important to note that some of the researchers have connections to the company that offers the test in the US and Europe—C2N Diagnostics.

The Diagnostic Challenge

All four blood tests aim to solve the problem of most people only being diagnosed with Alzheimer’s after they begin to show symptoms such as confusion or forgetfulness. These tests detect several proteins associated with the disease in order to identify people who may have Alzheimer’s earlier. According to the National Institute on Aging (NIA), prior to the early 2000s, patients were only definitively diagnosed with AD or another kind of dementia after they had died and an autopsy had been performed, but biomarkers, along with a variety of other tools are now available to more accurately determine someone’s risk for AD and reach a conclusive diagnosis sooner.

However, there is a key problem with biomarkers. While the NIA identifies them as an important tool in assessing someone’s risk for AD, most research on such Alzheimer’s biomarkers has been done with mainly White participants, meaning tests based on these biomarkers may not be as effective at identifying potential signs of the disease in other races, a press release on the Neurology study points out. This is a critical oversight, as, according to the Alzheimer’s Association, elderly Black Americans are around twice as likely to have AD or other types of dementia as White Americans, while elderly Hispanics are around one and a half times as likely to have AD or other dementias as elderly Whites. Currently, there are an estimated 6.5 million people in the US aged 65 and older living with AD, with that number projected to grow to 12.7 million by 2050, the Alzheimer’s Association says.

The Study

The Washington University School of Medicine in St. Louis research aimed to explore these concerns by assessing the performance of four blood tests in 76 pairs of African American and non-Hispanic White individuals (152 people in total), who were matched by cognitive status, APOE ε4 carrier status, and age. APOE ε4, the ε4 allele of the apolipoprotein E (APOE) gene, is a strong genetic risk factor for late onset AD. In the study, researchers collected blood and cerebrospinal fluid (CSF), looking for various Alzheimer’s biomarkers. The team:

• Performed amyloid positron emission tomography (PET) in 103 participants
• Measured plasma Aβ42/Aβ40 by a high-performance immunoprecipitation-mass spectrometry assay—C2N Diagnostics’ PrecivityAD
• Measured plasma p-tau181, p-tau231, and neurofilament light chain (NfL) by Simoa immunoassays

The team used CSF Aβ42/Aβ40 and amyloid PET status as primary and secondary reference standards of amyloid protein buildup in the brain (brain amyloidosis), respectively. Brain amyloidosis increases the risk of developing AD.

Findings

They found that models predicting brain amyloidosis that are based on plasma p-tau181, p-tau231, and NfL “may perform inconsistently and could result in disproportionate misdiagnosis of [African Americans],” while those that use a high-performance plasma Aβ42/Aβ40 assay “may provide an accurate and consistent measure of brain amyloidosis across [African American] and [non-Hispanic White] groups.”

What it Means

Because the number of participants in the study was small, and several team members have connections to C2N Diagnostics, more research will be needed to confirm the results. It’s also important to note that such biomarker blood tests only determine the chances that people may develop AD and are only one of many different tools used to assess someone’s risk of developing the disease. However, if further research confirms the results of the study, it would have important implications for the use of blood biomarker tests in certain racial groups, potentially helping clinicians choose the most accurate options for their patients and test makers improve their products.