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The typical test done in the UK at least only tells you the chance, and cannot always be performed. The only test that gives you certainty also carries a risk o
by IanCal 9y ago
The typical test done in the UK at least only tells you the chance, and cannot always be performed. The only test that gives you certainty also carries a risk of miscarriage.
It is not as simple as you make out.
- GordonS 9y ago> The only test that gives you certainty also carries a risk of miscarriage Not true any more[1]. See my other comment in this thread about the Harmony/NIPT test (it's not available on the NHS tho, but is widely available at a cost of around £400). [1] https://fetalmedicine.com/harmony-test https://fetalmedicine.com/harmony-test
- IanCal 9y agoI think the detection rates are significantly different. Your link shows that for trisomy 18 there's a 3% false negative rate with the Harmony test. I think the false negative rates are significantly lower for CVS.
- GordonS 9y agoCVS is indeed very accurate (97.5-99.6%[1]), but still has a false positive rate of ~1%[2]. But as you noted, CVS has a small risk of miscarriage, and for that reason many couples wouldn't even consider it. Of course I can't speak for everyone, but I would guess that for most couples the biggest concern is T21 (it is the most common of the three), and the NIPT test is 99% accurate for that. Balancing the risks, and false positive and negative chances of NIPT vs CVS, NIPT seems more valuable to me. [1] https://patient.info/doctor/chorionic-villus-sampling-pro https://patient.info/doctor/chorionic-villus-sampling-pro [2] Mayo Clinic Complete Book of Pregnancy & Baby’s First Year. Johnson, Robert V., M.D., et al, Ch. 11.
- IanCal 9y agoThanks. Are there figures for the false negative rate? I was struggling to find those. It's certainly a reasonable option, but the context of the original comment saying that the parent would have known (or had the option to know) that the child had T18.
- GordonS 9y agoI didn't find false negative figures specifically mentioned as such for CVS or NIPT, only accuracy and false positive. I've assumed false negative == 100 - accuracy, but in reality results might also sometimes be "uncertain", which wouldn't count towards the false negative rate.