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Dr. Isaacson:
Welcome to the Frontline of Alzheimer's Care, where we provide answers to burning questions from real clinicians about amyloid-targeting therapies in Alzheimer's disease. I'm Dr. Richard Isaacson, and I'm here with doctors Gayatri Devi and Pierre Tariot, to help answer these questions.
Let's hear a question from Dr. Chong.
Dr. Chong:
One of the main difficulties in making the diagnosis of Alzheimer's disease versus the mimics and the other dementias has been the lack of a completely objective biomarker, or at least one that's covered by insurances. So we know about amyloid PET but it costs several thousand dollars out of pocket. CSF can be invasive and maybe still not perfectly interpretable; there's a lot of in-between still. And then serum tests look promising, but they're not yet validated. So what biomarker or biomarkers would you most rely on before starting an amyloid-targeted therapy? And I'm curious, what do you think is next on the horizon? What's going to be available through insurance next?
Dr. Isaacson:
Well, this is a field that's rapidly moving. It feels like almost every couple of weeks or a couple of months, we have a new blood test and a new this and a new that. And then, of course, insurance coverage is going to be changing potentially very soon.
Dr. Tariot, what are your thoughts? If you can review the data and give us some perspective?
Dr. Tariot:
Yeah, just at a high level, what I would say is that the Centers for Medicare and Medicaid Services did recently announce that they are going to cover amyloid PET for people who have suspected Alzheimer's disease causing MCI or mild dementia, and actually opened the door to serial scans for people to be tracked over time, especially on anti-amyloid therapy. There are several FDA approved ligands for this purpose. So I think that's quite a game changer.
I think it's worth noting that the National Institute on Aging and Alzheimer's Association have recently updated their recommendations, at least for kind of a research framework. They recommend diagnosing Alzheimer's pathology, establishing the presence of it with either an amyloid PET scan or cerebrospinal fluid testing phosphorylated tau species, that epitope 217 and 181 and 231. And actually, they opened the door to use of plasma biomarkers for those exact p-tau species thinking that the analytical requirements have probably been met sufficiently, at least for research purposes. I don't have a crystal ball, but I would guess that we're at maybe a year or at probably, at most 2, before there are FDA approved plasma biomarkers to be used for this purpose.
Dr. Isaacson:
Well, that was a really great overview. And I think, you know, kind of sticking with the gold standard of either a spinal tap or an amyloid labelled PET scan prior to initiating an anti-amyloid therapy is just, I believe, really necessary at this point.
And I think as our field develops we're may not just look at one of these just for diagnostic purposes, but to also track basically response to therapies and, you know, is the tau going down? Is the amyloid changing? Are there other markers of neurodegeneration or neuroinflammation that we can track more easily using blood tests? So while the blood tests may not fully be all there yet in the next 1 to 2 to 3 years I think that may change.
Dr. Devi, what are some of your thoughts? You do this every day, every week in your practice. How do you think about this?
Dr. Devi:
I've been fairly cautious in terms of my definition of Alzheimer's disease. So in addition to objective evidence of cognitive impairment, I also require that patients have amyloid on imaging, and in most patients I require tau. So, the reason being that there are about 40% of cognitively normal people over the age of 60, have some level of amyloid deposit in the brain. So you want to make sure that the patients you're treating do in fact have amyloid have evidence of Alzheimer's. So I generally will have them get CSF evaluation for tau.
Dr. Isaacson:
Well, that's great. I think this part of our field is as rapidly moving, if not more so than the new FDA approvals that have come and that may come in the future. So I think this is a really exciting, exciting time in our field.
So with that, thank you to Dr. Chong, for such an important question. And for viewers who want to learn more, check out our other episodes about the clinical use of amyloid-targeting therapies. Thanks so much for joining me.
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