Same old question about DEXA accuracy
Chose that title because I suspect this may be a trite topic. But I've distilled it as best I can in case anyone new wants to see it.
I get an x-ray for osteoporosis. It’s called a DEXA.
DEXA indicates osteoporosis, I go on meds and have another DEXA a year later, same clinic, same room.
New DEXA shows dramatic improvement, however the numbers look weird. I ask my doc.
Great doc—he agreed the numbers are weird and didn’t know, so he sent me to an osteoporosis specialist.
Specialist—after about 20 minutes of confusion, it turned out the clinic I got my DEXA scans at switched to a different machine. Same make and model, but not the same machine. The tiny serial number on the X-ray images gave it away.
Specialist—we don’t know if you improved or not, you can’t compare the results of ANY two DEXA machines. We'll know after your scan next year if they still have this new machine.
Me—Wait. You’re telling me that if I had, say, ten DEXA scans on the same day on ten different machines, even with the same make and model, the results would all be different?
Specialist—Yes. You have to use the same machine to track changes.
Me—Then how do I know I even had osteoporosis to begin with?
Specialist—Your original DEXA scan showed it.
Me—Look. If you measure the same thing with ten different machines and get ten different numbers, at least nine of them are wrong. There is no way around this, it’s irrefutable logic. If ALL DEXA machines are expected to give different results of the same measurement, then they’re all wrong, unless one happens to be right by random chance. So with that in mind—how do I know I have any bone density issues at all, let alone how mild or severe they are?
Specialist— Medical stuff, unclear. (I wasn’t able to get an answer that made sense to me or that even sounded like it answered the question. Nobody seems to have an answer that satisfies. So I am on a powerful medication that can have serious side effects, to treat an illness that was diagnosed with a measurement known to be wrong. And so is everyone else being treated based on a DEXA scan. I’m not saying I don’t have bone loss—I’m saying I don’t KNOW if I do, or how much if there is some, and I don’t think anyone else diagnosed by DEXA does, either.)