A quick personal story. I have a treatable autosomal dominant condition. For the non-geneticists, that means any of my children have a 50% chance of exhibiting the trait. Even aggressive treatment is not usually initiated until one is in elementary school. But we want to know now, just so we can know (we plan to have more children soon, so we want to anticipate medical expenses or lack thereof, and well, just to know). When my wife went to the doctor today for a routine checkup for my daughter she asked for a blood test to confirm that my daughter exhibited, or did not, exhibit the symptoms (this is not a common SNP for what it's worth). Though the doctor was skeptical of the effectiveness of the test at this age, she also (according to my wife) decided to give my wife a lecture on the appropriateness of testing. Here's what my wife emailed me:
"she then spent a lot of time educating me about how you (read SHE) wouldn't ever want to know the status on something like that that you knew was a distinct genetic possibility up until right at the moment when you were going to take a therapeutic or preventative step if the status was positive."
God knows how the doctor would treat someone who was from a less socially advantaged group, or who was not college educated (and wasn't married to someone who knows a bit about medical genetics). Addendum: To be clear, there was going to be a blood draw for another reason, and so she just wanted this extra test added to the panel. It's a pretty standard test for adults, so I know it's doable.