4 ms·

A blood test accurately diagnosed Alzheimer's 90% of the time, study finds

46 points by m463 2y ago

toomuchtodo 2y ago
Study: https://jamanetwork.com/journals/jama/fullarticle/2821669 https://jamanetwork.com/journals/jama/fullarticle/2821669 Gift link: https://www.nytimes.com/2024/07/28/health/alzheimers-blood-test.html?unlocked_article_code=1.-k0.qdpV.fYnYeCJwap4Y&smid=url-share https://www.nytimes.com/2024/07/28/health/alzheimers-blood-t... (courtesy u/bookofjoe) Previous: https://news.ycombinator.com/item?id=41117254 https://news.ycombinator.com/item?id=41117254 https://news.ycombinator.com/item?id=41099517 https://news.ycombinator.com/item?id=41099517 https://news.ycombinator.com/item?id=41094443 https://news.ycombinator.com/item?id=41094443 Related: https://www.cnn.com/2024/07/28/health/alzheimer-blood-test-p-tau-217-wellness/index.html https://www.cnn.com/2024/07/28/health/alzheimer-blood-test-p... https://news.ycombinator.com/item?id=41094571 https://news.ycombinator.com/item?id=41094571
Rhapso 2y ago
To summarize the paper more technically: In a large cohort of patients with cognitive decline symptoms, it predicted with 90% accuracy which patients are determined by specialists to have Alzheimer's. This is in contrast to a 60% correct diagnosis rate by general practitioners. The test has both 90%+ specificity and sensitivity. The proposal is that this could improve the overall diagnostic rate by GPs by giving them a blood test to use when they are suspicious of Alzheimer's.
- nrr 2y ago
  "The test has both 90%+ specificity and sensitivity." This by itself feels like a big deal, even if we strip away the Alzheimer's context. Do we have a lot of blood tests that are both sensitive and specific to this degree?
  - tptacek 2y ago
    Seems important as a clinical substitute/adjunct for existing diagnostics (especially because they suck for other reasons), but the base rate for Alzheimers is just 10%, so like, you couldn't really run this on a whim, right?
    - nrr 2y ago
      I mean, part of the reason why I ask this question is that specificity and sensitivity tend to be inversely related: as a test becomes more sensitive, it tends to become less specific, say. (While I'm here, in case folks are lacking the statistics background: specificity and sensitivity refer to the probabilities that a test will return with a negative test result in the absence of a condition or a positive test result in the presence of a condition respectively.) Most of the "promising" tests I've seen tend to be something like 80% sensitive and 20% specific (testing for Lyme disease comes to mind), which makes them no better than flipping a weighted coin. The fact that this Alzheimer's test beats that feels like a big deal on the probability merits alone, and I can't think of basically any other tests that do that. (Serum cardiac troponins maybe?)
      - Rhapso 2y ago
        They don't offer any tests for "general population" situations, only "people we think might already have dementia". This is a really strong filter up-front. I suspect the test would be high sensitivity very low specificity in the general population, but that is an intuition not backed by any data.
        nrr 2y ago
        Aha, yeah, restricting your population could certainly have that effect on the specificity. Thanks for clarifying.
        tptacek 2y ago
        For what it's worth, I'm not sure specificity/sensitivity is the limiting factor here (for doing broad population surveys with this test); it's the low base rate of Alzheimers relative to the specificity. At 90% true positive and 10% base rate, I think? (I suck at math) a positive test has like a coin flip chance of being right?
elromulous 2y ago
https://archive.is/Hduyw https://archive.is/Hduyw
wileydragonfly 2y ago
The specter of dementia frequently makes me want to not live all that long.
deleted 2y ago
[deleted]
asp_hornet 2y ago
There is a dead comment which is actually quite interesting: > The specter of dementia frequently makes me want to not live all that long. What’s the point of knowing you’re probability of Alzheimers if there is no cure or means to delay it. Its just a shadow constantly looming over you and can be used in the future to deny you opportunities.
- Tepix 2y ago
  We already know of many factors that delay Alzheimer's, there are likely new ones to be found as well.
  - asp_hornet 2y ago
    Aplogies, i know very little about the subject. I just went by the article: > Testing recommendations could change if scientists find drugs that can delay or halt Alzheimer’s pathology in people who have not yet developed cognitive problems. But for now, said Dr. Boxer, “most of us feel like it would not be ethical to use it in people who don’t yet have symptoms, unless it’s in the context of a research study.”
y-c-o-m-b 2y ago
This is fantastic and a great step in the right direction, especially with the new treatments (mentioned in the article also). Unfortunately we still have doctors that either do not care enough or are not skilled enough to order simple blood tests. Me, my wife, and my father all have various auto-immune issues. It's been a frustrating fight on all three fronts to get any sort of testing done. For myself this has spanned over a decade now. My dad's journey is just starting, but we've had to switch specialists numerous times to get one that would actually DO something. For my wife, we begged two previous PCPs for years to get an ANA and rheumatoid factor panel done because I suspected she had rheumatoid arthritis. Those tests are simple and more importantly, they're cheap. No reason to not do them in the context of patient's complaints about chronic pain, especially if they provide peace of mind and rule out serious causes. PCPs consistently brushed it off as anxiety and stress. We finally found a new PCP to take it seriously, so lo and behold: positive blood tests for both ANA and Rheumatoid Factor! It's absurd that we have all these tools available to us, but they're not being utilized in many valid cases where they'd be useful. So while the article mentions this would be a way to start treatment early by detecting the disease earlier, I have low confidence in the health system to take that initial step.
- rrsp 2y ago
  For context Rheumatoid Factor is present in 4% of the healthy population, an even upto 30% in certain populations like native Americans [1] ANA is positive in 15% of the population [2] The idea that the tests rule out serious causes is not really correct, people can have seronegative inflammatory arthritis in which case these tests are negative. Peace of mind is dubious as well given that even with a positive test you are still more likely to not have an inflammatory arthritis. It’s a common misconception that blood tests are binary and provide concrete answers. Sometimes they do. But most blood tests, like many measurements, are far from binary and have a distribution across the normal population, once it passes an arbitrary threshold it does not necessarily mean you have disease X, context (clinical history and examination) are often far more important in making a diagnosis. Unfortunately some of the population tend to overweight blood tests vs a physicians assessment, I guess they see the former as an objective measure and the latter as subjective. Especially because if you shop around enough clinicians you’ll eventually find one who will say what you want to hear and that one will inevitably be ‘right’. 1. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3845430/ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3845430/ 2. https://rheumatology.org/patients/antinuclear-antibodies-ana# https://rheumatology.org/patients/antinuclear-antibodies-ana...
ChrisArchitect 2y ago
[dupe] Some more discussion: https://news.ycombinator.com/item?id=41094571 https://news.ycombinator.com/item?id=41094571

46 points by m463 2y ago

Study: https://jamanetwork.com/journals/jama/fullarticle/2821669 https://jamanetwork.com/journals/jama/fullarticle/2821669 Gift link: https://www.nytimes.com/2024/07/28/health/alzheimers-blood-test.html?unlocked_article_code=1.-k0.qdpV.fYnYeCJwap4Y&smid=url-share https://www.nytimes.com/2024/07/28/health/alzheimers-blood-t... (courtesy u/bookofjoe) Previous: https://news.ycombinator.com/item?id=41117254 https://news.ycombinator.com/item?id=41117254 https://news.ycombinator.com/item?id=41099517 https://news.ycombinator.com/item?id=41099517 https://news.ycombinator.com/item?id=41094443 https://news.ycombinator.com/item?id=41094443 Related: https://www.cnn.com/2024/07/28/health/alzheimer-blood-test-p-tau-217-wellness/index.html https://www.cnn.com/2024/07/28/health/alzheimer-blood-test-p... https://news.ycombinator.com/item?id=41094571 https://news.ycombinator.com/item?id=41094571

Rhapso 2y ago

To summarize the paper more technically: In a large cohort of patients with cognitive decline symptoms, it predicted with 90% accuracy which patients are determined by specialists to have Alzheimer's. This is in contrast to a 60% correct diagnosis rate by general practitioners. The test has both 90%+ specificity and sensitivity. The proposal is that this could improve the overall diagnostic rate by GPs by giving them a blood test to use when they are suspicious of Alzheimer's.

nrr 2y ago
"The test has both 90%+ specificity and sensitivity." This by itself feels like a big deal, even if we strip away the Alzheimer's context. Do we have a lot of blood tests that are both sensitive and specific to this degree?
- tptacek 2y ago
  Seems important as a clinical substitute/adjunct for existing diagnostics (especially because they suck for other reasons), but the base rate for Alzheimers is just 10%, so like, you couldn't really run this on a whim, right?
  - nrr 2y ago
    I mean, part of the reason why I ask this question is that specificity and sensitivity tend to be inversely related: as a test becomes more sensitive, it tends to become less specific, say. (While I'm here, in case folks are lacking the statistics background: specificity and sensitivity refer to the probabilities that a test will return with a negative test result in the absence of a condition or a positive test result in the presence of a condition respectively.) Most of the "promising" tests I've seen tend to be something like 80% sensitive and 20% specific (testing for Lyme disease comes to mind), which makes them no better than flipping a weighted coin. The fact that this Alzheimer's test beats that feels like a big deal on the probability merits alone, and I can't think of basically any other tests that do that. (Serum cardiac troponins maybe?)
    - Rhapso 2y ago
      They don't offer any tests for "general population" situations, only "people we think might already have dementia". This is a really strong filter up-front. I suspect the test would be high sensitivity very low specificity in the general population, but that is an intuition not backed by any data.
      - nrr 2y ago
        Aha, yeah, restricting your population could certainly have that effect on the specificity. Thanks for clarifying.
        tptacek 2y ago
        For what it's worth, I'm not sure specificity/sensitivity is the limiting factor here (for doing broad population surveys with this test); it's the low base rate of Alzheimers relative to the specificity. At 90% true positive and 10% base rate, I think? (I suck at math) a positive test has like a coin flip chance of being right?

elromulous 2y ago

https://archive.is/Hduyw https://archive.is/Hduyw

wileydragonfly 2y ago

The specter of dementia frequently makes me want to not live all that long.

deleted 2y ago

[deleted]

asp_hornet 2y ago

There is a dead comment which is actually quite interesting: > The specter of dementia frequently makes me want to not live all that long. What’s the point of knowing you’re probability of Alzheimers if there is no cure or means to delay it. Its just a shadow constantly looming over you and can be used in the future to deny you opportunities.

Tepix 2y ago
We already know of many factors that delay Alzheimer's, there are likely new ones to be found as well.
- asp_hornet 2y ago
  Aplogies, i know very little about the subject. I just went by the article: > Testing recommendations could change if scientists find drugs that can delay or halt Alzheimer’s pathology in people who have not yet developed cognitive problems. But for now, said Dr. Boxer, “most of us feel like it would not be ethical to use it in people who don’t yet have symptoms, unless it’s in the context of a research study.”

y-c-o-m-b 2y ago

This is fantastic and a great step in the right direction, especially with the new treatments (mentioned in the article also). Unfortunately we still have doctors that either do not care enough or are not skilled enough to order simple blood tests. Me, my wife, and my father all have various auto-immune issues. It's been a frustrating fight on all three fronts to get any sort of testing done. For myself this has spanned over a decade now. My dad's journey is just starting, but we've had to switch specialists numerous times to get one that would actually DO something. For my wife, we begged two previous PCPs for years to get an ANA and rheumatoid factor panel done because I suspected she had rheumatoid arthritis. Those tests are simple and more importantly, they're cheap. No reason to not do them in the context of patient's complaints about chronic pain, especially if they provide peace of mind and rule out serious causes. PCPs consistently brushed it off as anxiety and stress. We finally found a new PCP to take it seriously, so lo and behold: positive blood tests for both ANA and Rheumatoid Factor! It's absurd that we have all these tools available to us, but they're not being utilized in many valid cases where they'd be useful. So while the article mentions this would be a way to start treatment early by detecting the disease earlier, I have low confidence in the health system to take that initial step.

rrsp 2y ago
For context Rheumatoid Factor is present in 4% of the healthy population, an even upto 30% in certain populations like native Americans [1] ANA is positive in 15% of the population [2] The idea that the tests rule out serious causes is not really correct, people can have seronegative inflammatory arthritis in which case these tests are negative. Peace of mind is dubious as well given that even with a positive test you are still more likely to not have an inflammatory arthritis. It’s a common misconception that blood tests are binary and provide concrete answers. Sometimes they do. But most blood tests, like many measurements, are far from binary and have a distribution across the normal population, once it passes an arbitrary threshold it does not necessarily mean you have disease X, context (clinical history and examination) are often far more important in making a diagnosis. Unfortunately some of the population tend to overweight blood tests vs a physicians assessment, I guess they see the former as an objective measure and the latter as subjective. Especially because if you shop around enough clinicians you’ll eventually find one who will say what you want to hear and that one will inevitably be ‘right’. 1. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3845430/ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3845430/ 2. https://rheumatology.org/patients/antinuclear-antibodies-ana# https://rheumatology.org/patients/antinuclear-antibodies-ana...

ChrisArchitect 2y ago

[dupe] Some more discussion: https://news.ycombinator.com/item?id=41094571 https://news.ycombinator.com/item?id=41094571