A Blood Test for Alzheimer’s?
Blood Biomarkers and the Future of Alzheimer Disease Risk Assessment
Seth Keller, MD
Summary: A recent JAMA study suggests that the blood biomarker p-tau217 may help estimate future risk of cognitive impairment in older adults who are still cognitively unimpaired. Dr. Seth Keller explains why blood-based biomarkers could become a more accessible first step in Alzheimer evaluation while emphasizing that biomarkers should support, not replace, a full clinical assessment.
A recent JAMA study provides new evidence that the blood biomarker phosphorylated tau 217, or p-tau217, may help estimate the future risk of cognitive impairment in cognitively unimpaired older adults. Among 2,684 participants, higher baseline p-tau217 levels were associated with greater risk of later cognitive impairment. At five years, estimated risk was approximately 12% in those with low p-tau217 levels compared with 38% in those with very high levels.
This is important because blood-based biomarkers are less invasive and potentially far more accessible than cerebrospinal fluid testing or amyloid PET. p-tau217 has shown particularly strong accuracy for detecting Alzheimer-related pathology.
In my own clinical practice caring for people with Alzheimer disease who do not have an intellectual disability, I have found biomarker testing useful as an adjunct to the clinical evaluation. In selected patients, I have used amyloid PET imaging to help determine whether Alzheimer-related amyloid pathology is present and to compare that finding with the patient’s history, cognitive and functional changes, neurological evaluation, and other imaging. I do not view any biomarker as a stand-alone diagnosis, but rather as another important piece of the clinical picture.
The emergence of p-tau217 is therefore especially interesting. Blood biomarkers may ultimately provide a more accessible initial step in Alzheimer evaluation, with amyloid PET or other testing used when additional confirmation is needed. Some prevention trials are already using blood biomarkers for screening followed by amyloid PET confirmation.
Important caution remains. These findings are not yet precise enough
NTG Note: This report was prepared by Seth Keller, M.D., Co-President of the NTG. The NTG continues to follow emerging evidence on Alzheimer’s disease biomarkers and disease-modifying therapies and their implications for adults with intellectual disability, particularly those with Down syndrome.
About the Author
Dr. Seth Keller specializes in the evaluation and care of adults with Intellectual and Developmental Disabilities (IDD) with neurologic complications. Dr. Keller is on the Executive Board of the Arc of Burlington County as well as on the board for The Arc of New Jersey Mainstreaming Medical Care Board. He is the co-president of the National Task Group on Intellectual Disabilities and Dementia Practices (NTG). He is also the founder and past chair of the Adult IDD Section with the American Academy of Neurology. Dr. Keller is actively involved in national and international IDD health education as a speaker, and webinar and workshop participant. He is a co-author on a number of articles and book chapters relating to aging and dementia in those with IDD.