Quest Diagnostics recently announced the launch of a direct-to-consumer blood test to detect amyloid plaques in the brain. The test examines the ratio of Ab42/Ab40 in the plasma. Based on the Quest website, the test results are provided in numeric fashion, as well as based on categories of low, intermediate, and high risk of amyloid presence in the brain (with lower numbers on the plasma Ab ratio associated with higher likelihood of amyloid being present in the brain). As can be seen on the website, there is a high degree of overlap on test results among those with elevated compared to not elevated amyloid (assessed with a brain PET scan, the current gold standard). It is not clear what proportion of results would be intermediate, which might also be considered “indeterminant.” The test costs $399 and is being marketed for repeated use for individuals to monitor their risk of AD.
Research into AD blood tests have exploded in recent years. The technology used in this offering from Quest is similar to previous tests, such as the Precivity test from C2N Diagnostics. New plasma tests, likely to enter practice in the near future, may hold even greater promise for higher precision and fewer indeterminant test results.
The main difference with this Quest plasma test is that it is being offered directly to consumers, rather than as a tool for expert clinicians to use as part of their work. We continue to believe that these tests are best used in the hands of expert clinicians, given that the implications of undergoing such tests and understanding their results are complex, multifactorial, and worthy of discussion with an expert.
In particular, the marketing of the new test, including quotes from a Quest medical director, indicate that they plan to make this test available to cognitively unimpaired individuals who are interested in better understanding their risk for Alzheimer’s disease in the future. This, for us, raises concerns.
We understand the desires of individuals to better understand their personal risk for cognitive impairment in the future. We are concerned, however, about the ramifications of supposed “presymptomatic” testing. In the research setting, biomarker testing in older unimpaired individuals has been safe and effective; the process to ensure participant understanding and to minimize negative psychological reactions was cautious and prescribed. The need for education and counseling before such testing is critical, and we are concerned that this will be inadequate with a direct-to-consumer test. Just as importantly, we do not yet live in a dementia-friendly society. The risks of stigma and discrimination for people deemed at increased risk based on these tests, many of whom will still be working and otherwise very active, are real and potentially serious. Lastly, as yet, there are no therapies to offer such individuals. On-going studies aim to test promising treatments as potential preventions, and will be key to changing current approaches to predictive testing. Lifestyle recommendations can be made to lower risk for dementia, but all people concerned about future cognitive impairment—regardless of these tests—can and should adhere to recommendations such as better diets, more exercise, and working closely with a physician to limit other risk factors such as a hypertension, high cholesterol, or poor sleep.
