The D.I.Y. way of getting a probability estimate from your doctor
May 6, 2011 20 Comments
One frustrating thing about dealing with doctors is that they tend to be unwilling or unable to talk about probabilities. I run into this problem in particular when they’ve told me there is “a chance” of something, like a chance of a complication of a procedure, or a chance of transmitting an infection, or a chance of an illness lasting past some time threshold, and so on. Whenever I’ve pressed them to try to tell me approximately how much of a chance there is, they’ve told me something to the effect of, “It varies” or “I can’t say.” I sometimes tell them, look, I know you’re not going to have exact numbers for me, but I just want to know if we’re talking more like 50% or, you know, 1%? Still, they balk.
My interpretation is that this happens due to a combination of (1) people not having a good intuitive sense of how to estimate probabilities and (2) doctors not wanting to be held liable for making me a “promise” – perhaps they’re concerned that if they give me a low estimate and it happens anyway, then I’ll get angry or sue them or something.
So I wanted to share a useful tip from my friend, the mathematician who blogs at www.askamathematician.com, who was about to have his wisdom teeth removed and was trying unsuccessfully to get his surgeon to tell him the approximate risks of various possible complications from surgery. He discovered that you can actually get a percentage out of your doctor if you’re willing to just construct it yourself:
Friend: “I’ve heard that it’s possible to end up with permanent numbness in your mouth or lip after this surgery… what’s the chance of that happening?”
Surgeon: “It’s pretty low.”
Friend: “About how low? Are we talking, like five percent? Or only a fraction of one percent?”
Surgeon: “I really can’t say.”
Friend: “Okay, well… how many of these surgeries have you done?”
Surgeon: “About four thousand.”
Friend: “How many of your patients have had permanent numbness?”
Friend: “Ah, okay. So, about one twentieth of one percent.”
Surgeon: “I really can’t give you a percentage.”