6 ms·

Some clarifications: "Half" here is the 10 year cumulative probability of at least one false positive if you get a screening each year. The status quo ten-yea

Some clarifications: "Half" here is the 10 year cumulative probability of at least one false positive if you get a screening each year. The status quo ten-year false positive rate with the test used before 3d mammograms (digital mammography) is 56.3, and the false positive rate with 3d mammograms (aka tomosynthesis) is 49.6. So the study is actually reporting an improvement vs the previous state of the art! It's weird that the article is written to convey that the false positive rate of the new technique is a drawback when it's actually a benefit. (This comment has been heavily edited thanks to a correction I received below.)

barbegal 5y ago
I think you've got the numbers mixed up according to the paper https://jamanetwork.com/journals/jamanetworkopen/fullarticle/2790521?utm_source=For_The_Media&utm_medium=referral&utm_campaign=ftm_links&utm_term=032522 https://jamanetwork.com/journals/jamanetworkopen/fullarticle... "tomosynthesis [3D mammogram] vs digital mammography [previous test] for all outcomes: 49.6% vs 56.3%"
- asdfasgasdgasdg 5y ago
  Yeah, I mixed up which name applied to the new technique. To be clear, I don't know the space, I just read the study and assumed that "digital mammography" sounded more 3d-ish than "tomosythesis". I'll update my comment accordingly. Edit: oh man. Now I see that I mixed up the direction too! What in the heck. The article was written like there was a big problem with 3d mammograms so I assumed it was performing worse on this metric than the baseline. But in fact it's better?
rkangel 5y ago
I think that the title is actually a pretty clear and accurate statement. [If you assume that all women have mammograms at the normal cadence, over a period of 10 years then] half of women will get a false positive.
- asdfasgasdgasdg 5y ago
  The title is technically accurate, but you have to take into account uninformed people's priors in order to efficiently convey information that might update their beliefs. Just my personal opinion on this issue. If you say "new technique [X] has [high] false positive rate," you're going to make people who don't know the status quo think there is a deficit in the new technique. Also, I'm not just talking about the title.
  - rkangel 5y ago
    Yes, the article seemed to be making two different points and got a little directionless as a result: * Half of all women will get false positives - that's a lot, it's not great, people will think they have cancer and we should set expectations * Despite the introduction of a newer technology to improve false positives (3D scanning) we've only improved the situation from 56% to 50%
    - labcomputer 5y ago
      > only improved the situation from 56% to 50% But isn't that millions of fewer false positive results over 10 years? Assumptions: * US Women: ~150e6 * Fraction getting annual mamograms: ~1/3 (life expectancy of 80yrs, and mamograms during 30 of those years, minus some with poor access to health care) * Reduction in cumulative FP rate over 10 year period: 6% 150e6 x 0.33 * 0.06 = ~3e6 fewer false positive results over a 10 year period. That seems like a significant effect size to me.
      - Dylan16807 5y ago
        It's significant but it's also pathetic. The false positive rate is really high.

barbegal 5y ago

I think you've got the numbers mixed up according to the paper https://jamanetwork.com/journals/jamanetworkopen/fullarticle/2790521?utm_source=For_The_Media&utm_medium=referral&utm_campaign=ftm_links&utm_term=032522 https://jamanetwork.com/journals/jamanetworkopen/fullarticle... "tomosynthesis [3D mammogram] vs digital mammography [previous test] for all outcomes: 49.6% vs 56.3%"

asdfasgasdgasdg 5y ago
Yeah, I mixed up which name applied to the new technique. To be clear, I don't know the space, I just read the study and assumed that "digital mammography" sounded more 3d-ish than "tomosythesis". I'll update my comment accordingly. Edit: oh man. Now I see that I mixed up the direction too! What in the heck. The article was written like there was a big problem with 3d mammograms so I assumed it was performing worse on this metric than the baseline. But in fact it's better?

rkangel 5y ago

I think that the title is actually a pretty clear and accurate statement. [If you assume that all women have mammograms at the normal cadence, over a period of 10 years then] half of women will get a false positive.

asdfasgasdgasdg 5y ago
The title is technically accurate, but you have to take into account uninformed people's priors in order to efficiently convey information that might update their beliefs. Just my personal opinion on this issue. If you say "new technique [X] has [high] false positive rate," you're going to make people who don't know the status quo think there is a deficit in the new technique. Also, I'm not just talking about the title.
- rkangel 5y ago
  Yes, the article seemed to be making two different points and got a little directionless as a result: * Half of all women will get false positives - that's a lot, it's not great, people will think they have cancer and we should set expectations * Despite the introduction of a newer technology to improve false positives (3D scanning) we've only improved the situation from 56% to 50%
  - labcomputer 5y ago
    > only improved the situation from 56% to 50% But isn't that millions of fewer false positive results over 10 years? Assumptions: * US Women: ~150e6 * Fraction getting annual mamograms: ~1/3 (life expectancy of 80yrs, and mamograms during 30 of those years, minus some with poor access to health care) * Reduction in cumulative FP rate over 10 year period: 6% 150e6 x 0.33 * 0.06 = ~3e6 fewer false positive results over a 10 year period. That seems like a significant effect size to me.
    - Dylan16807 5y ago
      It's significant but it's also pathetic. The false positive rate is really high.