Several years ago a young man visited my clinic and requested a “complete set of blood tests”. I asked what he meant by that. He clarified that he wanted “all available blood tests done”. I asked why he wanted such information and he confidently asserted that he just wanted to be sure that there was nothing wrong with him. We spent some time discussing blood tests and I gently tried to explain that he very likely did not have enough money to run every conceivable test that could be purchased at that time. When I tried to explain why that would not be a good idea anyway, the conversation became a little more difficult. Ultimately, I endeavored to explain the statistical concept of pre-test probability. I find that this concept is poorly understood by many people.
More here. It’s a good message, but at the time I read the post, I caught two errors in it, both serious. I noted them in the comments to the post. So, if after reading the post, you’re confused, read the comments. (Oddly, all my comments are entered twice even though I only did so once.)
This, by the way, is why expansion of home testing is potentially problematic.
