. Detection of β-amyloid positivity in Alzheimer’s Disease Neuroimaging Initiative participants with demographics, cognition, MRI, and plasma Biomarkers. Brain Communications, February 2, 2021

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  1. The data on blood tests for AD, both Aβ42/Aβ40 and pTau isoforms, are quite exciting to me as both a researcher and a clinician. Algorithms that incorporate individual-level factors (e.g., age, sex, APOE genotype, race) and multiple biomarkers are likely to be very powerful, and potentially much more predictive on an individual level than the traditional single-cut-off model. 

    I completely agree that we should test these biomarkers in large cohorts that are representative of the broader population. However, I would note that dementia specialists have been using CSF biomarkers and amyloid PET in select patients for well over a decade, without the benefit of massive datasets across many groups—and most dementia specialists and patients have found this information to be accurate and useful. 

    Given the rapid rate of development of blood-based biomarkers, do we really need to wait five years to incorporate them into clinical care? Is it reasonable to set the threshold for blood test accuracy so high, when the threshold for CSF biomarkers and amyloid PET was so much lower?

    Very few patients with memory complaints (likely <5-10 percent) currently get AD biomarker testing because of cost and availability issues. A blood test could enable AD biomarker testing in the majority of patients with memory complaints. Would setting a very high threshold for an AD blood test mean that more patients are misdiagnosed, because for many patients, the real-world alternatives may be an AD blood test or no biomarker testing at all?

    We should absolutely validate AD blood tests carefully to minimize inaccurate results, but waiting too long and setting too high a bar could also have negative consequences for all the patients who never get a biomarker test. Hopefully we can refine and test these assays expeditiously so that our patients can benefit sooner rather than later. But for the sake of our patients, we should also consider that sometimes the perfect is the enemy of the good. Or in this case, that having a very good AD blood test is a better alternative than the current status of most dementia patients, who have no AD biomarker testing at all. 

    View all comments by Suzanne Schindler

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