← Back to context

Comment by brandonb

14 hours ago

This Alzheimer's blood test, PrecivityAD2, is based on the p-tau217 biomarker.

In one recent study, people very high p-tau217 had a 38% chance of progressing to cognitive impairment within 5 years vs 12% for those with low levels. The current tests cost about $200-300, so they're not unreasonable as a screening test. PrecivityAD2 looks to be priced around $1,400-$1,500 so at that price, this specific test likely only makes sense for people with established disease.

That sounds pretty expensive for me for a test with that low accuracy, especially when there's not much you can do different if it comes back high vs. coming back low.

  • From TFA:

    > Early detection of Alzheimer’s disease is important since the first treatments capable of slowing the progression of the neurodegenerative disease recently became available to patients, and these drugs are more effective when started sooner rather than later. Other promising investigational drugs are in the pipeline.

    A very good friend's wife had Alzheimer's caught early, and the medication she's on stopped its progression. It's much better for her than my family members who had no treatment options.

    • I am not personally aware of any treatment for which there is particularly compelling evidence that it meaningfully slows progression even when started early. I wish there was.

      It’s also not clear that one can measure progression well enough that an n=1 data point is meaningful. And I’m also far from convinced that very early Alzheimer’s that would progress rapidly enough to be noticeable can be detected with enough specificity to rule out fairly common cases of people who test positive but effectively don’t have the disease.

      Best wishes to your friend’s wife.

      1 reply →

  • Agreed that we can't do as much as we'd like. There are some general health things that are believed to prevent cognitive decline, such as managing cholesterol, HbA1c, blood pressure, sleep apnea, etc. One phrase I've heard is that cholesterol at age 50 predicts cognitive health at age 70.

    But hopefully we'll start to have more options and wider approvals for things like anti-amyloid drugs.

    • Hi there. Actually, Leqembi is a 1st gen Alzheimer’s drugs and targets amyloid plaques. But, like other responses, amyloids doesn’t seem to be hugely responsible for Alzheimers, which is why targeting things like tau proteins is being explored.

    • > anti-amyloid drugs

      Isn’t the viewpoint in the last decade that amyloid plaques are likely a finding rather than the underlying cause of Alzheimer’s Disease?

      5 replies →

  • It sounds similar to Lipoprotein(a) blood test for cardiac risk.

    It's (almost) purely determined by genetics. You can't do anything to improve it, other than to improve every other cardiac related risk factor.

    (There are some experimental drugs in the pipeline, though)

    • There is an oral PCSK9 treatment (enlicitide) was recently released that provides a 30% reduction, and of course you can't get insurance coverage without the test. And there are 2 drugs with 90%+ reduction in Lp(a) in phase3 trials with expected release in 2027-8, in particular Olpasiran.

  • I guess you can start spending your retirement money faster

    • I know it’s a joke but then you’ll leave your family bearing the burden of your care. As someone whose parents had dementia, finding a place that treats your parents with dignity is extremely expensive and very rare. We were spending 12k/month and even we needed to set up camera’s and my sister slept with my mom and took care of her like a nurse. When the pandemic hit my sister couldn’t enter so every morning they took my mom, clothed her and sat her facing the bathroom all day long.

      The only other alternative is some sort of mental hospital which is more like a prison than anything else.

      2 replies →

    • The sad fact is that some people really should. Many people find it far easier to be or become indigent and fall on Medicaid services. If you do not qualify for Medicaid, then there is a real possibility that your insurance carrier will help put you or your caregivers into massive debt for a long-term illness like this.

      If you do go into long-term care, Medicaid will probably seize your assets to help pay for everything. For example, a house in your name. They'll use those to pay back what they paid for your care.

      So if you're gonna get sick and you're gonna be a burden in your old age, best to plan for leaving this world the way you came in: naked and penniless.

We can also test for PSEN1, which is 100% accurate in determining early onset alzheimer's disease, quite a it more expensive, so unreasonable as a screening tool unfortunately.

That price difference seems like the key point. A $200 test can plausibly be used to decide who should get further workup; a $1500 test is already competing with the cost of the workup itself

  • From a medical perspective, what's the point of the initial test or the workup though? Is it just to check a box? If it comes back positive you will be told to exercise, eat well, take sleep seriously, and manage cholesterol. If it comes back negative you will be told to do the same things.

    I've seen up close what dying with these kinds of illnesses look like. For me, a positive test would be a sign that it may be time to say my goodbyes and plan my exit.

    • I do think telling you to get your affairs in order and to arrange for hospice care is probably good for the doctors. They don't want a family coming in with a sudden decline case and all the information about how to pay for it lost, at minimum

epistemics asks how many different hypotheses besides p-tau217 levels were tested before arriving at the specified spread.

  • Are you suggesting that these research scientists don't understand basic statistics?

    • While I’ve nothing to say about these research scientists in particular, knowing precisely nothing about them, it wouldn’t be the first time that so-called ‘bonafide’ research scientists made a statistical boo-boo, even one structural to the research thesis than any sort of math error.

      Given the widely-reported extent of p-hacking in the biomedical literature over the decades, I’m surprised anyone would float an avid ‘but how could research scientists ever be wrong’ default reflex.

      1 reply →