Finally, a Blood Test for Dementia?

Written By: Dr. Marc Rothman

This year’s Alzheimer’s Association International Conference featured an exciting new study that inspired veteran attendees.

We are taught in medical school that examination of the post-mortem brain is the only way to definitively diagnose Alzheimer’s disease. However, a July 2020 study in the Journal of the American Medical Association revealed that the blood biomarker P-tau217 can differentiate Alzheimer Disease, both in-progress but also potentially decades before its onset.      

In the short-term, this blood test is a potential game-changer for clinical trials of drugs that target AD. There are many significant barriers to the enrollment of qualified participants in Alzheimer’s Disease clinical trials. In fact the Pharmaceutical Research and Manufacturers of America (PhRMA) has stated that this itself is “the greatest obstacle to developing new Alzheimer’s treatments.”  Some of these considerations include:

  • Primary care physicians (PCPs) are busier than ever and don’t have the bandwidth or the interest to stay on top of research opportunities.
  • Research has shown that PCPs may not be aware of diminished cognition in over 40% of their cognitively impaired patients.
  • Many of the studies require participants to have a partner who can record symptoms and daily behaviors. In the U.S., about 800,000 of the 5-million individuals with Alzheimer’s live alone.
  • Cognitive assessments usually take hours and can be draining for individuals who are not cognitively diminished      
  • Sometimes invasive procedures like lumbar punctures are required just to qualify for a study.
  • Folks from diverse racial and ethnic backgrounds are not represented for the same reasons we discussed in “Dementia’s Racial and Ethnic Divide.”

The P-tau217 biomarker, if appropriately validated and made available for clinical trials, means that pharmaceutical companies no longer have to play the odds by qualifying participants based on subjective data alone. A definitive blood test bulldozes all but one of the above-mentioned barriers to entry and enables the inclusion of pre-symptomatic individuals, which means a substantially larger and more qualified pool of participants than ever before.

On a personal level, the study raises issues we have long grappled with. What if you knew for sure that you were destined to get AD over the next ten to twenty years? People whose parents have a definitive diagnosis of Alzheimer’s will be able to determine that they are in line to get it in the future. On the plus side, you will potentially be motivated to take better care of yourself, you can alert your children to your wishes, and eventually, there will be preventive medications you can take that prevent or delay dementia far better than the ones available now. On the negative side, there may be a long delay between when you can learn this information and when those drugs are available, which will cause an awful lot of anxiety and fear. 

All of this is to say that the P-tau217 biomarker is fertile soil for the development of drugs that prevent Alzheimer Disease. We are still years away from reaping that harvest so in the meantime the best medicine is to stay fit, exercise regularly, keep your blood pressure and cholesterol in check, stay connected to loved ones, and never stop stimulating your brain and your senses.         


JAMA (Journal of the American Medical Association) Network, “Discriminative Accuracy of Plasma Phospho-tau217 for Alzheimer Disease vs. Other Neurodegenerative Disorders,” Palmqvist, Janelidze, Quiroz, et al., July 2020

NCBI Resources, “Obstacles and Opportunities in Alzheimer’s Clinical Trial Recruitment,” Watson and Bernard, et al., April 2014

National Library of Medicine, “Physician Recognition of Cognitive Impairment: Evaluating the Need for Improvement,” Chodosh et al., July 2004

BrightFocus Foundation, “When a Parent Lives Alone and Has Alzheimer’s: It Takes a Village,” Kathleen Allen, January 2020

The contents and information on DementiaSpring.Org are for educational purposes only and is not intended to substitute for medical advice, diagnosis or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition.

Any opinions expressed about, or endorsements of persons, services or organizations are solely those of Dementia Spring and are not made on behalf of Signify Healthcare or any other entity.

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