3 ms·

The point of this is not that you get a definitive diagnosis; it's just a somewhat reliable marker on whether you may need to be concerned and get more accurate

by axxto 5y ago

The point of this is not that you get a definitive diagnosis; it's just a somewhat reliable marker on whether you may need to be concerned and get more accurate (but more harmful) imaging or invasive tests to rule out something.

dangerlibrary 5y ago
You only need one false positive test result that ends up with a colonoscopy to understand how costly and uncomfortable these errors can be. (I'm using an uncomfortable and illustrative example, but a colonoscopy is honestly pretty safe and boring as invasive clinical diagnostic procedures go)
- theptip 5y ago
  Perhaps a better example than you intended -- recently colonoscopies are being considered more risky as a regular screening tool, because the procedure itself can result in harms, including (rarely) death. Not an expert here, but it seems they are still used in a fairly wide age group, but the recent trend is to be more cautious about their usage, as particularly for older patients they are more risky vs. the potential benefits. [1] However I think this concern would be reduced if we had better first-line screening like the tests in TFA; the harms come from using a relatively-risky assay like colonoscopy for regular screening in healthy individuals, whereas if we had better noninvasive screening, the colonoscopy could be reserved for patients where there's a higher probability of a positive diagnosis. [1]: https://jamanetwork.com/journals/jama/fullarticle/2529486 https://jamanetwork.com/journals/jama/fullarticle/2529486
bcrosby95 5y ago
> somewhat reliable marker For the USA... Something around 1.8 million people are diagnosed with cancer per year. At a 50% false negative rate, all else being equal it would detect 900k of those. And all else being equal, at a 0.5% false positive rate, if it were used as suggested it would incorrectly diagnose cancer in around 1.6 million of the population. So around 60% of the people it says has cancer wouldn't have cancer. I guess it depends upon what you mean by "somewhat reliable".
colinmhayes 5y ago
You don't see how causing many people to worry and get invasive screening per person you have a true positive for is a worse outcome?

by axxto 5y ago

dangerlibrary 5y ago

You only need one false positive test result that ends up with a colonoscopy to understand how costly and uncomfortable these errors can be. (I'm using an uncomfortable and illustrative example, but a colonoscopy is honestly pretty safe and boring as invasive clinical diagnostic procedures go)

theptip 5y ago
Perhaps a better example than you intended -- recently colonoscopies are being considered more risky as a regular screening tool, because the procedure itself can result in harms, including (rarely) death. Not an expert here, but it seems they are still used in a fairly wide age group, but the recent trend is to be more cautious about their usage, as particularly for older patients they are more risky vs. the potential benefits. [1] However I think this concern would be reduced if we had better first-line screening like the tests in TFA; the harms come from using a relatively-risky assay like colonoscopy for regular screening in healthy individuals, whereas if we had better noninvasive screening, the colonoscopy could be reserved for patients where there's a higher probability of a positive diagnosis. [1]: https://jamanetwork.com/journals/jama/fullarticle/2529486 https://jamanetwork.com/journals/jama/fullarticle/2529486

bcrosby95 5y ago

> somewhat reliable marker For the USA... Something around 1.8 million people are diagnosed with cancer per year. At a 50% false negative rate, all else being equal it would detect 900k of those. And all else being equal, at a 0.5% false positive rate, if it were used as suggested it would incorrectly diagnose cancer in around 1.6 million of the population. So around 60% of the people it says has cancer wouldn't have cancer. I guess it depends upon what you mean by "somewhat reliable".

colinmhayes 5y ago

You don't see how causing many people to worry and get invasive screening per person you have a true positive for is a worse outcome?