Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

When they warn of rare disorders, these prenatal tests are usually wrong

nytimes.com

Post reply on HN
Print view View original

41–50 of 176 posts

Re: When they warn of rare disorders, these prenatal tests are usually wrong

#41

Post by isoprophlex »

halpert wrote: post #30
SpicyLemonZest wrote: post #25

Earlier quoted context omitted.

Their infographics convince me that they understand the statistics. But one of the key issues here is that the statistics are radically counterintuitive in a way that most people don't understand - the patients, the testing companies, and even some medical staff all incorrectly believe that a positive test for a rare condition means you probably have the condition.

Their graphics say the tests are “84% wrong.” Do you really feel that’s an accurate description? That doesn’t feel like an accurate description to me, and their usage of “wrong” in this context highlights that they don’t understand the distinction and importance of true positives, false positives, true negatives, and false negatives when measuring accuracy.

Going through something like this is very VERY stressful. When you get a negative you immediately forget about it. When you get a positive you die inside. Speaking from experience here.

84% wrong sounds, to me, as an accurate description. Experiencing this from the inside out, only the false/true positive ratio matters. (Given sufficiently low false negative rates, of course)

84% of people whose world is turned upside down are actually getting a wrong diagnosis.

Re: When they warn of rare disorders, these prenatal tests are usually wrong

#43

Post by isoprophlex »

inglor_cz wrote: post #5

Interesting. We have been undergoing IVF with my wife since 2019. (Covid made a huge mess of those plans...) One of our embryos tested as a possible positive (but only slightly) for aneuploidy of one chromosome. The doctor, a veteran of IVF, looked at the results and said "my experience is that this is either a very small mosaic error, which tends to be utterly invisible in real life, or a computer artifact. I have n…

Good luck, keep up your hope. I hope things work out for you.

Re: When they warn of rare disorders, these prenatal tests are usually wrong

#44

Post by [deleted] »

isoprophlex wrote: post #41
halpert wrote: post #30

Earlier quoted context omitted.

Their graphics say the tests are “84% wrong.” Do you really feel that’s an accurate description? That doesn’t feel like an accurate description to me, and their usage of “wrong” in this context highlights that they don’t understand the distinction and importance of true positives, false positives, true negatives, and false negatives when measuring accuracy.

Going through something like this is very VERY stressful. When you get a negative you immediately forget about it. When you get a positive you die inside. Speaking from experience here. 84% wrong sounds, to me, as an accurate description. Experiencing this from the inside out, only the false/true positive ratio matters. (Given sufficiently low false negative rates, of course) 84% of people whose world is turned upsid…

[deleted]

Re: When they warn of rare disorders, these prenatal tests are usually wrong

#45

Post by isoprophlex »

don-code wrote: post #31

I am not a parent, but the criticism of the article appears to be around a misunderstanding of statistics, or at least how to apply them. While I agree that criticism is completely correct, it overlooks the human nature of the people receiving the tests. At an already-stressful point in someone's life, it seems almost like bad bedside manner for the medical community, even if in an automated fashion, to tell people t…

I totally agree with this. Managing perceptions and expectations is super important here.

Having been on the receiving end of a false positive, I'd still do the test again for a hypothetical future pregnancy. Even though it was hell for a couple of days.

Re: When they warn of rare disorders, these prenatal tests are usually wrong

#46

Post by sterlind »

I've heard that in the early days of HIV, the tests were (e.g.) 95% accurate, and when patients saw their positive results and the supposed 5% chance it's wrong they'd sometimes kill themselves.

They revised the tests so the first test would say Inconclusive rather than Positive, and ask them to repeat it. This saved some lives.

Maybe this a UX failure? Shouldn't the test designers present the results like this, even to doctors?

Re: When they warn of rare disorders, these prenatal tests are usually wrong

#47

Post by ramraj07 »

halpert wrote: post #40
ellisv wrote: post #36

Earlier quoted context omitted.

I disagree. It is clear from the title, “When They Warn of Rare Disorders, These Prenatal Tests Are Usually Wrong”, and the lead that they’re focusing on false positives.

It's true they are focusing on false positives, but the authors are using the ratio of false positives to true positives to paint a picture that the tests are inaccurate, when in reality the tests are accurate. What this article is looking at is called the "sensitivity" of a test: https://en.wikipedia.org/wiki/Sensitivity_and_specificity

Did they use the word accurate? You used the word accurate and then you yourself are going on a tirade about how that’s not correct?

It’s clear the article is talking about why sensitivity is important in layman’s terms and while it could use better writing it’s a real problem in diagnostics. This is why you don’t ask men to take a pregnancy test to check for prostrate cancer. It is accurate but not sensitive.

Re: When they warn of rare disorders, these prenatal tests are usually wrong

#48

Post by adjkant »

halpert wrote: post #40
ellisv wrote: post #36

Earlier quoted context omitted.

I disagree. It is clear from the title, “When They Warn of Rare Disorders, These Prenatal Tests Are Usually Wrong”, and the lead that they’re focusing on false positives.

It's true they are focusing on false positives, but the authors are using the ratio of false positives to true positives to paint a picture that the tests are inaccurate, when in reality the tests are accurate. What this article is looking at is called the "sensitivity" of a test: https://en.wikipedia.org/wiki/Sensitivity_and_specificity

While the author may not be well versed or focusing on the stats side, you're missing the human side here I think.

> the tests are inaccurate, when in reality the tests are accurate

If the test make someone consider terminating a pregnancy or even considering it, that's a lot of pain. So for that human, the test is failing its purpose potentially, depending on the value calculation of terminating a viable pregnancy vs the severity of the issue if it comes to term.

For a human, accuracy as you defined it means little to nothing. Usefulness and helpfulness are far better metrics, and such a high false positive rate is clearly causing issues in respect to those, which is what the article is highlighting.

Re: When they warn of rare disorders, these prenatal tests are usually wrong

#49

Post by halpert »

ramraj07 wrote: post #47
halpert wrote: post #40

Earlier quoted context omitted.

It's true they are focusing on false positives, but the authors are using the ratio of false positives to true positives to paint a picture that the tests are inaccurate, when in reality the tests are accurate. What this article is looking at is called the "sensitivity" of a test: https://en.wikipedia.org/wiki/Sensitivity_and_specificity

Did they use the word accurate? You used the word accurate and then you yourself are going on a tirade about how that’s not correct? It’s clear the article is talking about why sensitivity is important in layman’s terms and while it could use better writing it’s a real problem in diagnostics. This is why you don’t ask men to take a pregnancy test to check for prostrate cancer. It is accurate but not sensitive.

They used the word “wrong”. Whether or not they used wrong to mean inaccurate, or wrong to mean not sensitive is up to the reader.

Re: When they warn of rare disorders, these prenatal tests are usually wrong

#50

Post by adjkant »

sterlind wrote: post #46

I've heard that in the early days of HIV, the tests were (e.g.) 95% accurate, and when patients saw their positive results and the supposed 5% chance it's wrong they'd sometimes kill themselves. They revised the tests so the first test would say Inconclusive rather than Positive, and ask them to repeat it. This saved some lives. Maybe this a UX failure? Shouldn't the test designers present the results like this, even…

Absolutely a UX failure here, one that it seems some doctors translate for patients while others are left in the dark on. From the way people are responding on here about the use of statistics in the article, it's clear that a big portion of the techo community I think is undervaluing that often UX is far more important than it is treated.
Post reply on HN