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Comment by hannob | Hacker News Reader

The reason this is not happening isn't a technical one. It's that people with a medical background will tell you this isn't a healthy utopia, it's a nightmare.

Medical tests are complicated. They often have significant false positive and false negative rates. Testing people at scale increases the number of people with wrong test results and can cause harm if you start treating people based on wrong test results. The more healthy people you test the more false positives you get.

The goal of evidence based medicine is to use tests when they can help. It's not to test as many people as possible. This is reasonable. You want to improve patient's lives. Whether or not a test is improving patient's lives is often not easy to answer and has to consider many things.

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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.

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)

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

> 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".

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?

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