4 ms·

Devil's advocate- Mammograms are a very useful diagnostic tool, but only when applied in the right circumstances because of the rate of false positives. It's r

Devil's advocate- Mammograms are a very useful diagnostic tool, but only when applied in the right circumstances because of the rate of false positives. It's recommended for 50+, but when given to a 30-year old, the results are meaningless in most cases (it becomes more likely to get a false positive than a real positive). Knowing when to take tests and interpreting test results are sometimes an important part of the test.

josephcsible 5y ago
Sure, a test wouldn't be very useful in that case. But I don't think you should be forbidden from taking a test at your own expense just because it's not useful.
- scoopertrooper 5y ago
  In the case of a false positive, a test is not merely useless, but actively harmful. Having said that, imposing an age restriction on at-home Mammogram testing kits would mitigate the problem. However, Mammograms are probably not the best choice for at-home testing given that they involve X-rays!
  - saurik 5y ago
    One doesn't need act on a false positive! It is useful to have that data point, and then you can combine it with tons of other data points, and do risk benefit analyses of whether to do anything at all about it even if you are feeling sure. You are assuming people are too stupid to even be allowed to know things, which is an unreasonable starting point.
    - brianpan 5y ago
      The fact that many people here (which I consider smarter and more informed than the average population) misunderstand this, I think proves my point. Mammograms under 50 give MORE false positives that real positives. That means it's not even a useful data point. If you have a positive result, it's you're more likely you do NOT have cancer than you do. You really have to understand your base rate of expected occurrence and the effectiveness of the test. These can wildly affect how to interpret the results and tell you if you should even take the test in the first place. Here's a somewhat related Numberphile about false positives: https://www.youtube.com/watch?v=M8xlOm2wPAA https://www.youtube.com/watch?v=M8xlOm2wPAA
      - josephcsible 5y ago
        I understand that, and I agree that people under 50 shouldn't get this test for that reason. I just think that if they want to anyway, the government shouldn't stop them.
light_hue_1 5y ago
This is absurd. Cancer is diagnosed incredibly late far too often. If we would dedicate capacity to screen much more often and much earlier we would be far better off and many more people would survive. The main issue with universal screening is cost. Medicine is far too expensive and now we need to divide up a scarce resource. The 2nd issue is subclinical cancers that would not kill you before you die of something else. But we don't spend much time on the 2nd issue because we don't screen as much as we could if we made healthcare cheaper.
- brianpan 5y ago
  It's not absurd, it's statistics. If you're trying to detect something that's fairly rare, it's very easy to have a test produce more false positives than real positives. That means if you randomly take a test and it has a positive result, it's more likely you do NOT have the cancer than do. More detection of cancer and earlier is great. But testing has it's limitations and the general public doesn't always understand the statistics involved to apply the tests correctly. https://www.youtube.com/watch?v=M8xlOm2wPAA https://www.youtube.com/watch?v=M8xlOm2wPAA
- KennyBlanken 5y ago
  No, the issue with universal screening is that many screenings return positive results but the patient never develops cancer. In the case of some cancer treatments, like prostate cancer, the treatment is invasive and life-alerting on its own. Further, some screening methods involve radiation exposure, and in large population groups, the effects of that additional radiation starts to have a significant effect and may overtake the delta between "screen who we estimate needs it" and "screen everyone", which means you've given cancer to more people, looking for cancer. Wrist injuries are a pain in the ass to x-ray looking for broken bones, but CT scans are very reliable. But...CT scans involve a _fuckton_ more x-ray exposure. They're also more time consuming, use much more expensive equipment, generate a lot more data, and require more work to analyze. So generally, ERs continue to use x-rays to check for broken wrist bones. Also, since you replied to a comment about breast cancer: breast cancer is among the most diagnosed, most successfully treated, and most survivable cancers. There is no scientific basis for easing or promoting more breast cancer screenings.
coderintherye 5y ago
True, but why are the results so poor for < 50 year-olds and what does that mean? [0] It seems like we as society should be tackling that problem and part of tackling that problem seems like getting more scans of denser breasts so we can develop better techniques for detecting cancer within them. Restricting access by age makes it so that we are optimizing detection for later age. Something has to change in our current approach to help figure that part of the problem out, perhaps loosening restrictions should be one such change. [0] https://www.breastcancer.org/research-news/20100727 https://www.breastcancer.org/research-news/20100727
- jbandela1 5y ago
  The reason the results are so poor in younger women, is that younger women have denser breasts. Mammograms work by picking up densities (which many times indicate a tumor. In younger women, the whole breast is dense and you really can't tell (especially with lower radiation doses). MRI can work, but it is much more expensive, and finding the exact location of the abnormality on MRI can be trickier.
causi 5y ago
Doing a self breast exam also has a much higher rate of false positives than real positives.

josephcsible 5y ago

Sure, a test wouldn't be very useful in that case. But I don't think you should be forbidden from taking a test at your own expense just because it's not useful.

scoopertrooper 5y ago
In the case of a false positive, a test is not merely useless, but actively harmful. Having said that, imposing an age restriction on at-home Mammogram testing kits would mitigate the problem. However, Mammograms are probably not the best choice for at-home testing given that they involve X-rays!
- saurik 5y ago
  One doesn't need act on a false positive! It is useful to have that data point, and then you can combine it with tons of other data points, and do risk benefit analyses of whether to do anything at all about it even if you are feeling sure. You are assuming people are too stupid to even be allowed to know things, which is an unreasonable starting point.
  - brianpan 5y ago
    The fact that many people here (which I consider smarter and more informed than the average population) misunderstand this, I think proves my point. Mammograms under 50 give MORE false positives that real positives. That means it's not even a useful data point. If you have a positive result, it's you're more likely you do NOT have cancer than you do. You really have to understand your base rate of expected occurrence and the effectiveness of the test. These can wildly affect how to interpret the results and tell you if you should even take the test in the first place. Here's a somewhat related Numberphile about false positives: https://www.youtube.com/watch?v=M8xlOm2wPAA https://www.youtube.com/watch?v=M8xlOm2wPAA
    - josephcsible 5y ago
      I understand that, and I agree that people under 50 shouldn't get this test for that reason. I just think that if they want to anyway, the government shouldn't stop them.

light_hue_1 5y ago

This is absurd. Cancer is diagnosed incredibly late far too often. If we would dedicate capacity to screen much more often and much earlier we would be far better off and many more people would survive. The main issue with universal screening is cost. Medicine is far too expensive and now we need to divide up a scarce resource. The 2nd issue is subclinical cancers that would not kill you before you die of something else. But we don't spend much time on the 2nd issue because we don't screen as much as we could if we made healthcare cheaper.

brianpan 5y ago
It's not absurd, it's statistics. If you're trying to detect something that's fairly rare, it's very easy to have a test produce more false positives than real positives. That means if you randomly take a test and it has a positive result, it's more likely you do NOT have the cancer than do. More detection of cancer and earlier is great. But testing has it's limitations and the general public doesn't always understand the statistics involved to apply the tests correctly. https://www.youtube.com/watch?v=M8xlOm2wPAA https://www.youtube.com/watch?v=M8xlOm2wPAA
KennyBlanken 5y ago
No, the issue with universal screening is that many screenings return positive results but the patient never develops cancer. In the case of some cancer treatments, like prostate cancer, the treatment is invasive and life-alerting on its own. Further, some screening methods involve radiation exposure, and in large population groups, the effects of that additional radiation starts to have a significant effect and may overtake the delta between "screen who we estimate needs it" and "screen everyone", which means you've given cancer to more people, looking for cancer. Wrist injuries are a pain in the ass to x-ray looking for broken bones, but CT scans are very reliable. But...CT scans involve a _fuckton_ more x-ray exposure. They're also more time consuming, use much more expensive equipment, generate a lot more data, and require more work to analyze. So generally, ERs continue to use x-rays to check for broken wrist bones. Also, since you replied to a comment about breast cancer: breast cancer is among the most diagnosed, most successfully treated, and most survivable cancers. There is no scientific basis for easing or promoting more breast cancer screenings.

coderintherye 5y ago

True, but why are the results so poor for < 50 year-olds and what does that mean? [0] It seems like we as society should be tackling that problem and part of tackling that problem seems like getting more scans of denser breasts so we can develop better techniques for detecting cancer within them. Restricting access by age makes it so that we are optimizing detection for later age. Something has to change in our current approach to help figure that part of the problem out, perhaps loosening restrictions should be one such change. [0] https://www.breastcancer.org/research-news/20100727 https://www.breastcancer.org/research-news/20100727

jbandela1 5y ago
The reason the results are so poor in younger women, is that younger women have denser breasts. Mammograms work by picking up densities (which many times indicate a tumor. In younger women, the whole breast is dense and you really can't tell (especially with lower radiation doses). MRI can work, but it is much more expensive, and finding the exact location of the abnormality on MRI can be trickier.

causi 5y ago

Doing a self breast exam also has a much higher rate of false positives than real positives.