I'm trying to sort out the reality of a closely related question. What are the statistics around actual damage done by false positives from discretionary screening? This is clearly a potential case, but obviously we won't ever know for sure.

My immediate family has two cases in which discretionary screening did or could have potentially have changed outcomes.

First case, I had purchased a $20 glucometer off of Amazon to just test my blood sugar. Device was stuffed in a drawer only to be found a year or two later. I gathered the family 'round to make a blood offering to medical science, and it turns out my youngest was over 2x the standard range. Follow up the next day and same, take her to the endo and she has Type I diabetes. The fact that it was detected before she went to the ER in full diabetic ketoacidosis was so unusual that I bet we told the 'discovery' story 20 or more times to nurses, two endocrinologists, her primary care physician and the folks at Medtronic. What the hell? This is a $.50 test that has good specificity and selectivity for something being wrong. +1 for discretionary screening.

Second case, my wife was complaining of abdominal pain for a few months. Her entire family hates going to doctors, but after much urging from me she heads to urgent care. They send her away with basically nothing. She develops a cough, goes back a month later, says the pain is from the cough and here is some cough medicine. Another month goes by and we end up in the ER because urgent care is closed. They do a CT and find softball sized masses on her ovaries. Two days later she is diagnosed with stage 3C ovarian cancer. Had someone taken the time to do an ultrasound or do her CA-125 tumor marker early on, this could have been detected sooner and possibly before she was stage 3. Two years later we're now probably a million dollars into medical treatments and she's still in the thick of it.
Again, in my estimation this is a +1 for discretionary screening.

The part that confuses me is that if you look at articles, papers and interviews with doctors, you'll find what seems to be a prevailing attitude in the medical community that discretionary screening causes stress, over-treatment and negative outcomes. Not only that, it happens so often that the benefits really need to be studied closely before any action is taken. Then, of course, these studies fall behind treatment studies in priority and as far as I can tell, don't get prioritized or completed.

My pet theory is that, in the US anyway, the medical community has an innate sense that there isn't nearly enough capacity to handle all of the incoming cases that would result, and because you can't blame a doctor for someone getting diabetes or cancer, they are off the hook. I'll stop short of saying it's a conspiracy, but in my opinion there is clearly some parallel thinking going on.

Happy to be proven wrong, though.

Edit: Here's an example. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3873201/

Summary of four large scale ovarian cancer screening trials >20K participants starting as early as 1987. Universal findings that TVS + CA-125 reduces staging at detection, which is one of the best predictors of outcome in ovarian cancer. Where is the clinical implementation? Reading through this it seems the perfect is the enemy of the good, and it's extremely frustrating. At $40 per TVS and $50 per CA-125, my wife's treatment so far could pay for 40 years of screening for 250 women.