The genius of non-invasive prenatal screening (NIPS) is NOT its 99% detection rate, because the screening test it replaced - a blood test combined with an ultrasound - was already nearly as sensitive (96%) for the detection of Down syndrome (We’re going to get wonky here, but remember that the detection rate/sensitivity is the percent of the time the test will come back ‘positive’ if the fetus has Down syndrome).
The genius of NIPS is that the false-positive rate for the detection of Down syndrome was incredibly low. Less than 1% compared to 5% for the test it replaced. That’s a big deal: it used to be that one in 20 women received a call from their doctor saying they were at high-risk for carrying a child affected by Down syndrome, even though in fact almost all of these fetuses were entirely normal. (False positive means the test returns ‘positive’ when the fetus is actually normal.)
(Neither the old test nor the newer tests were quite as good at detecting the much rarer trisomies 13 and 18 that are part of the basic panel, but NIPS is better than the older test and both of these diagnoses are essentially always apparent on ultrasound just a few weeks later.)
Had testing companies stopped there and offered NIPS for trisomies 13, 18, and 21 alone, the current loss of confidence, publicized by the New York Times on Jan 1, and called out by the FDA in an April 19 safety notice, would have been avoided entirely. Women would have access to a better test. Full stop. (Disclosure reminder to check my profile: I used to work for one of these companies.)
But a testing arms race started: companies started to compete with each other to offer additional tests for microdeletions and other super-rare genetic abnormalities, even though the detection rates were low and the false positive rates were high. Critically, every test added increased the chance that the patient would get the dreaded call: your screening test shows your fetus is high risk for a genetic abnormality.
Which leads to the leadership dilemma: doctors wanted to provide their patients with more testing options, and either didn’t understand or didn’t care that the more expansive tests were irresponsible (to put words in the FDA’s mouth). The laboratory companies knew the expansive tests performed poorly (many of these data are published and are included in test brochure fine print). But demand fueled sales, and encouraged labs to offer more and more options. What would it have taken for a leader at one of the major genetic testing companies to stick with a limited, highly reliable test at the expense of sales?