sithu

I wanted to add my thoughts about false positives and executive health checkups, which fall under the larger umbrella of screening. I conduct executive checkups fairly regularly, but i’m not promoting anything here. I just want to share a personal philosophy that you, as a patient, could adopt to reduce risk.

Firstly, it should be stated that the utility and performance of any diagnostic test that has a binary outcome (eg. diseased/healthy) depends on 1) its intrinsic test characteristics 2) the prevalence of the disease in the population being tested[1], 3) the available diagnostic/treatment options for positive people, and 4) the threshold chosen to call something ‘positive’ since you are virtually always measuring a continuous variable.

People talk about false positives often, but you should know that there is some room for judgement here. The typical threshold for PSA has historically been 4.0 ng/mL. Above this is considered a positive screen, and you are recommended further testing to confirm prostate cancer, which can be invasive and lead to complications (bleeding, nerve damage, etc). This kind of two-stage testing is a common theme. The issue is that PSA values in people with cancer and people without cancer are normally distributed and have some overlap. A value of 4.0 is in the overlap zone, and the vast majority of people with 4.0 will not have cancer. However, lets say hypothetically that guidelines changed and we now use 20. At this level, most people who test positive probably have something bad, and the risk:benefit ratio is in favor of confirmatory testing and probably in favor of treatment too. I won’t bother going into it, but there’s a fair amount of liability, psychology and economics at play when choosing thresholds. Biochemical tests like PSA do have some variance, but are mostly reliable. It’s more complicated with imaging and amorphous things like mammograms that have some operator variability in judgement (and hence more liability).

This was a long-winded way to say that information is not necessarily bad, but it’s what you and your doctor choose to do with it. There’s room for discussing probabilities, and the various available pathways. Trust is huge. Your doctor will act in your best interests when he feels safe from lawsuits, otherwise he'll be focused on not missing anything regardless of likelihood or cost. The financial misalignment of our system doesn’t help in building trust either. Most first-stage screening tests have very minimal risk involved. Things like checking your blood pressure, cholesterol, glucose, doing a treadmill stress test, reviewing your meds, vaccinations, etc which are part of these annual checkup programs are, on balance, usually good ideas.

Most HIPAA recommendations seem to be a good idea to do anyway.

Cars aren't going anywhere anytime soon in the US because sadly you can't function without one in the vast majority of places. It's far easier to implement this design philosophy for a growing city[1], but really hard to change the layout of a mature one, though it can be done thoughtfully [2].