https://xkcd.com/1132/ seems appropriate. Or perhaps https://xkcd.com/2545/
When they warn of rare disorders, these prenatal tests are usually wrong
81–90 of 176 posts
Re: When they warn of rare disorders, these prenatal tests are usually wrong
#82My wife and I went through this a couple of years ago, with a 10 week NIPT calling a rare trisomy (chr 9), which is always fatal within a few weeks of birth. It was absolute hell. The key problem here is the waiting and uncertainty. You have the NIPT at 10w, but you can’t have the amniocentesis until several weeks later. When that came back fine, there were questions about whether it was a “mosaic” meaning only a sma…
Having gone through two twin pregnancies (where the odds of these tests being correct are especially low) we declined all of them. Anecdotally, I know of several parents who had a positive test for genetic disorder, went ahead with the pregnancy anyway and children were perfectly healthy. Until these tests are close to 100% reliable I don’t see the point.
The point is that it is a screening test. A positive test will be followed by a more invasive test that has a lower false positive rate.
Re: When they warn of rare disorders, these prenatal tests are usually wrong
#83Earlier quoted context omitted.
> implicit calls for the FDA to Do Something and ban the tests (not an iota of cost-benefit considered nor any self-reflection about whether we want the FDA involved in anything at all these days)... This is true in so many areas of journalism but lately seems especially egregious in the NYT. And I don't really blame them, as the incentives for any individual reporter are just too great - having the government make a…
"the incentives for any individual reporter are just too great - having the government make a major policy change based on your article is basically the brass ring for an investigative reporter" Yep, this is the framing I came here looking for. Investigative journalists live in the same asymmetrically-incentivized world as social science researchers. If the reporter had looked into the phenomenon and concluded "yeah,…
I wonder if the NYT editorial staff receives zillions of these pitches from their reporters purporting to reveal nefarious phenomena, and most of them turn out benign. It's fun to imagine that the NYT editorship is actually exceedingly good at detecting these outrage-false-positives before publication, but the base rate of outrage-true-positives is just so low that you have to expect some to make it to publication.
I'd like to imagine there's an investigative-journalism-editor-news somewhere, and they're discussing this discussion saying "bah, these clowns are making sweeping generalizations about editorial standards based on only a false positive; this is totally specious with no mention of the prior distribution or sensitivity vs specificity trade-offs"
Re: When they warn of rare disorders, these prenatal tests are usually wrong
#84My 2nd daughter was flagged during our 20 week for something having to do with the way her skull was forming and they wanted to do a series of genetic test. They charged us through the wazoo and everything came back negative. She arrived 3.5 weeks early and contracted bacterial meningitis shortly after birth. We found her code blue in the crib. She ended up having a bilateral craniotomy to relieve the empyema that ha…
I am sorry for your horrible situation.
I don’t really understand what your implication is. Are you wishing you had not done the genetic tests? Suggesting you should have aborted the 20-week fetus based on unusual skull appearance? Suggesting that the meningitis was a result of some malpractice? Mad at medical professionals who are now “dropping hints” without saying something more substantive?
The problem with these tests highlighted (confusingly) by the NY Times article is that they test for extremely rare conditions but have a high enough false positive rate (by my napkin math, on order 0.05% = 1/2000 false positive rate) that they end up dramatically over-diagnosing these conditions.
That doesn’t necessarily mean the people designing the tests were lacking in “sound science” or were behaving maliciously. Their tests just need to be almost perfect to not overdiagnose rare abnormalities, and perfection in medical tests is a very high bar. Arguably we shouldn’t do tests for such rare conditions unless the false positive rate can be dropped by another order of magnitude or more, and if we do such tests communication to those who test positive should be much clearer. On the other hand, since genetic abnormalities are so life altering, even a 10% or 20% chance of an accurate positive might be grounds to abort a very early fetus.
It sounds like your specific problem was that the genetic tests did not return a positive result, even though it seems plausible that your child had some genetic abnormality. Not picking up every possible genetic condition is a different problem from the false-positive problem highlighted by the article.
Re: When they warn of rare disorders, these prenatal tests are usually wrong
#85My wife and I went through this a couple of years ago, with a 10 week NIPT calling a rare trisomy (chr 9), which is always fatal within a few weeks of birth. It was absolute hell. The key problem here is the waiting and uncertainty. You have the NIPT at 10w, but you can’t have the amniocentesis until several weeks later. When that came back fine, there were questions about whether it was a “mosaic” meaning only a sma…
Having gone through two twin pregnancies (where the odds of these tests being correct are especially low) we declined all of them. Anecdotally, I know of several parents who had a positive test for genetic disorder, went ahead with the pregnancy anyway and children were perfectly healthy. Until these tests are close to 100% reliable I don’t see the point.
"it worked out fine for me" is not particularly reassuring when the alternative is a lifetime of medical bills and possibly a permanent dependent.
Re: When they warn of rare disorders, these prenatal tests are usually wrong
#86Earlier quoted context omitted.
So you are saying the testing companies in the article aren't fraudulently claiming much more effective tests than they are providing?
Specificity and sensitivity are two dimensions that you can measure tests in. You can claim your test is 99% accurate if you mean that "if the test says you don't have the disease, there is a 99% chance that you don't have the disease". That same test can still be 85% wrong if it says you DO have the disease, though. I doubt that hyping one side of this equation is fraud. Pushing the error in this direction seems lik…
Here's the fliers mentioned in the article:
https://www.harmonytest.com/content/dam/RMS/harmonytest/glob...
https://web.archive.org/web/20211116203541/https://myriadwom...
https://images.health.questdiagnostics.com/Web/QuestDiagnost...
I'd appreciate it if you could point out where any of them walk the potential customer through sensitivity, specificity, and the fact that if they test positive, there is an 80-90% chance that their will not be affected. I can't seem to find any of that.
Re: When they warn of rare disorders, these prenatal tests are usually wrong
#87My 2nd daughter was flagged during our 20 week for something having to do with the way her skull was forming and they wanted to do a series of genetic test. They charged us through the wazoo and everything came back negative. She arrived 3.5 weeks early and contracted bacterial meningitis shortly after birth. We found her code blue in the crib. She ended up having a bilateral craniotomy to relieve the empyema that ha…
I am sorry for your horrible situation. I don’t really understand what your implication is. Are you wishing you had not done the genetic tests? Suggesting you should have aborted the 20-week fetus based on unusual skull appearance? Suggesting that the meningitis was a result of some malpractice? Mad at medical professionals who are now “dropping hints” without saying something more substantive? The problem with these…
I've always wondered-- is the error between tests correlated? Why does it not suffice to gather all the positive outcomes and test them again, then again and again until you have sufficient power depending on the rarity of the disease in the population? I know that for covid tests for example the test outcome errors aren't independent, which is why even taking several tests you can't be confident you're negative even if you tested negative. But I figured that was a special case and it was because their error comes from variance in viral load or something. But would that apply to these genetic marker tests?
Re: When they warn of rare disorders, these prenatal tests are usually wrong
#88My 2nd daughter was flagged during our 20 week for something having to do with the way her skull was forming and they wanted to do a series of genetic test. They charged us through the wazoo and everything came back negative. She arrived 3.5 weeks early and contracted bacterial meningitis shortly after birth. We found her code blue in the crib. She ended up having a bilateral craniotomy to relieve the empyema that ha…
I am sorry for your horrible situation. I don’t really understand what your implication is. Are you wishing you had not done the genetic tests? Suggesting you should have aborted the 20-week fetus based on unusual skull appearance? Suggesting that the meningitis was a result of some malpractice? Mad at medical professionals who are now “dropping hints” without saying something more substantive? The problem with these…
[deleted]
Re: When they warn of rare disorders, these prenatal tests are usually wrong
#89My 2nd daughter was flagged during our 20 week for something having to do with the way her skull was forming and they wanted to do a series of genetic test. They charged us through the wazoo and everything came back negative. She arrived 3.5 weeks early and contracted bacterial meningitis shortly after birth. We found her code blue in the crib. She ended up having a bilateral craniotomy to relieve the empyema that ha…
I am sorry for your horrible situation. I don’t really understand what your implication is. Are you wishing you had not done the genetic tests? Suggesting you should have aborted the 20-week fetus based on unusual skull appearance? Suggesting that the meningitis was a result of some malpractice? Mad at medical professionals who are now “dropping hints” without saying something more substantive? The problem with these…
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Re: When they warn of rare disorders, these prenatal tests are usually wrong
#90Earlier quoted context omitted.
I am sorry for your horrible situation. I don’t really understand what your implication is. Are you wishing you had not done the genetic tests? Suggesting you should have aborted the 20-week fetus based on unusual skull appearance? Suggesting that the meningitis was a result of some malpractice? Mad at medical professionals who are now “dropping hints” without saying something more substantive? The problem with these…
Quoted post unavailable.
you should probably step back and take a breather.
youre emotionally involved in a matter with your kid(s) - as one should be - but thats not the way to have a public discourse.