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

Considering this as a UX challenge - imagine a grid of 10,000 dots (100x100).

Draw one box around the base rate - the rate at which you expect to find the problem in the population. If the base rate is 1%, then the box is 10x10 = 100 dots.

Then color in the dots for the test positive rate (not false positive, just all positive tests) False positives would be the colored dots outside the box.

Next to that, put strikes through the dots corresponding to your expected false negative rate.

"A 2014 study found that 6 percent of patients who screened positive obtained an abortion without getting another test to confirm the result."

Maybe people aren't informed enough. It is my experience that some doctors tend to cut conversations short and some people are shy/insecure enough not to pry answers out of them.

In this case, that would be a tragedy, given that statistically 5 of those 6 aborted fetuses were healthy.

Edit: I found the following comment in the comment section of this article, which appears to address the same issue:

I am a physician with a PhD in Biomedical Informatics. Most patients who receive these tests do not see a maternal fetal medicine doctor or genetic counselor, and no one actually explains that the tests they are receiving are “screening” or “diagnostic.” Your opinion that this article does a disservice to patients reflects your unrealistic assumption that most of the doctors ordering these tests are actually communicating effectively with patients (or frankly, even understand the tests themselves). In my experience, they usually aren’t/don’t. Articles like this “fill the gap” on patient education when doctors are unable to explain math and risk (i.e., most of the time).

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 small proportion of cells are effected. We were only really in the clear after the 20 week ultrasound.

That’s a lot of weeks to be consumed by wondering about whether to terminate the pregnancy, or wait it out for more information. I have a masters in bioinformatics (in genomics!) and my knowledge of stats and the science was next to useless in the face of these decisions.

I know of couples who simply couldn’t deal with this uncertainty and chose to terminate on the basis of this test alone.

Fortunately for us our child was fine and is a perfectly healthy 18 month old now, but I wouldn’t do the rare trisomy test again.