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Comment by ethhics | Hacker News Reader

From [0], the types of cancer they can screen make up at least 81.4% of new cancer diagnoses, which means that with their 99.4% true positive rate, this test should be able to correctly identify ~80% of new cancer incidences. If I'm doing my math right, that's really impressive.

[0]: https://www.wcrf.org/dietandcancer/cancer-trends/worldwide-c...

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It seems to have a great false positive rate, but a not-good false negative rate. It misses the bulk of stage one cancers. So its utility for early diagnosis (the important bit) is marginal at this time.

For those not in the lab business: a low false positive rate and a high false negative rate are useful for confirmatory testing, not for screening. Such tests are terrible for screening. So this might be able to insert itself between the screening test (e.g. mammo, psa, or CXR) and the biopsy, but it won't replace the biopsy because you still have to characterize the cancer for further treatment decisions.

From a market positioning standpoint, it's not bad, because you don't piss off the generalist physicians by stealing their screening role, and you don't piss off the pathologists or surgeons by stealing their biopsies. The question is, does it add sufficient value for the payer to pay?

> For those not in the lab business: a low false positive rate and a high false negative rate are useful for confirmatory testing, not for screening. Such tests are terrible for screening.

Newbie question: wouldn't a test with very few false positives, but frequent false negatives, still be good for screening if it was cheaper/easier than existing screening, so it could be given to more of the population based on a weaker suspicion threshold? Like, in the limit of it being free and having zero false-positive rate, you'd give it to everyone.

(Maybe given your expertise it's obvious to you that the test is sufficiently expensive that this argument doesn't apply?)

Frequent false negatives mean it will miss many people who do have the disease, leading them to believe they are healthy until the disease progresses to a point it may be more difficult to treat.

If you're kicking people with cancer out of the medical system on a screening test, you're going to have a bad day.

If the mam (or other image) is positive for cancer, this test wont stop them doing a biopsy.

exactly, which begs the question of why would a payer pay this?

Many of these early cancers are asymptomatic and universal diagnostic imaging in the absence of symptoms is cost prohibitive. Better blood tests address that and other important gaps.

If you start testing asymptomatic people, healthy people, even a 1% false positive rate is tricky.

You’d follow an asymptomatic false positive blood test with at worst a whole body MRI and at best a targeted imaging study (if the blood markers are specific). You’d have a further false positive rate from that but it drops off quickly. The cost is manageable. And some of that cost is offset because you catch cancers earlier when they are less expensive to treat. A substantial cost savings will come through first line analysis of imaging by AI, to highlight images for radiologists to focus on.

But if the tests are cheap enough you can repeat them and compare. Bringing cost of blood diagnostics down is I think a good idea. I have fitness and health conscious friends who regularly get direct-to-consumer tests as a matter of course. In a few cases they have caught issues very early.

This is understanding there are some false positives, but being able to recognize them and learn to ignore them is better than not testing out of fear you overreact.

Repeating a test doesnt help. The blood result likely wont be different the second time. A false negative is a person for whome the test just doesnt work, no matter how many times you repeat it. (In reality, these sorts of important tests are run multiple times against the single sample before they print the results.)

For a simple false negative it would. That is a special false negative, at least to me. Is that occurrence common, and do you have an example?

How so they determine false negatives? Are there other less broad and more expensive test?

That said, isn't it also possible at Stage 1 for the body to cure itself? That is, __in theory__ is it possible Stage 1 defecation is too early? That med intervention could be premature?

You test for false negative rate by testing known cancer patients. A patient with cancer, but a clean test, is a false negative.

I think you meant detection—and not defecation—right?

Yeah. Oops. Autocorrect FTL

It also identifies cancers where early detection usually makes a life and death difference. Like esophageal and pancreatic and probably others.

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