Confusion in DEXAland

This a follow-up to two previous posts about my experiences with DEXA scans:
http://bit.ly/2BQlpEC
http://bit.ly/2YDvu2x

When I was in high school, my parents were friends with a couple called Bob and Marge. In old age Marge, a small, sweet-faced woman, developed catastrophic bone loss and was forced to wear a sort of metal cage to hold her body together. She was in constant pain and spent much of her time in bed.

Osteoporosis is a real and serious condition that can destroy your life if it gets out of hand. At this point, the only therapy accepted by the medical establishment is a group of drugs called bisphosphonates, which are not all that effective and should probably not be used long term because of an increasing risk of side effects such as fractures of the femur and osteonecrosis of the jaw. In order to avoid taking bisphosphonates, I have been using a program of impact exercises for the hip and spine, initially based on research by Dr. Larry Tucker at Brigham Young, as described in the previous two posts.

The decision to start bisphosphonate therapy should not be taken lightly. This is why it is so important for there be clear, consistent, and reliable data on the patient’s actual condition, both in the present and as time goes on. This year, as every year, after the DEXA had been completed, I asked the technician to print me a copy of the report from the machine. (Copies of pages from the 2019 and 2018 reports are included in this post.) I immediately noticed that my spine, which had been shown as osteoporotic since 2015, was now back in osteopenia territory; it had improved by one whole standard deviation within the past year.



The technician told me that this year’s report would look different from last year’s because this year the machine (modestly named the Lunar Prodigy Advance DXA System) had read L1-L4 instead of the L1-L2 it had looked at last year. I asked whether the change was an actual improvement or whether it was just a statistical artifact because the machine was looking at four vertebrae instead of two and she said it was an actual improvement. She also alerted me to the fact that the machine would now go back and change the numbers from all the spine readings of previous years so that the 2019 and 2018 reports would not match up. The hip readings for both years were about the same.

Looking at page 1 of each of the two, the 2018 report said that my spine was osteoporotic at 0.798 g/cm² whereas the 2019 report says that the 2018 reading was osteopenic at 0.931 g/cm². It also revises the WHO Classifications to show osteopenia for all past years, even though previous reports have shown osteoporosis in the spine since 2015. The % Change vs. Previous column shows no significant change in the past year!

How to make sense of this? It appears to me that machine is looking at two different dimensions of spine health and bringing them together, rather awkwardly, on page 1. This looks like poor scientific practice. What is really serious, though, is that it conceals the improvement in my spine from anyone to doesn’t actually look at the two reports side by side.

The radiologist probably didn’t do this. The linear structure of electronic health records means that the 2018 report was probably buried about fifteen screens down. Who has time to scroll through all that—and why bother when the report appears to be giving you the information you need already? A week later a nurse from my doctor’s office called to say that my doctor was recommending I take a bisphosphonate. I pointed out that my spine seemed to have improved and that my hip readings were stable. My guess is that the radiologist recommended the drug in order to be protected from liability and my own doctor, who probably didn’t have time to look at one report much less two, just took his or her word for it.

I still wanted to know what had prompted the Lunar Prodigy to look at two additional vertebrae so I emailed GE, the manufacturer. No response. I’m reserving judgment until next year about the big improvement in my spine but I do believe that the exercises are protecting my spine and hip bones at least as well as bisphosphonates would and without the added risks.