DEXA machines are not all the same!

Yes, this I experienced myself. Definitely made me question my diagnosis.
Lumbar Spine
10/2023 TScore -2.7 (0.855) GE Lunar
01/2025 TScore -3.5 (0.659) Hologic
11.7% BMD Change (attributing to different machine)
No way I lost that much BMD in 14 months, especially when during 2024 I had all the tests run to determine no other reason for bone loss other than menopause.

Hologic spinal bone mineral density (BMD) values and T-scores are systematically lower—typically 11% to 20% lower—than those measured on GE Lunar systems.

So, does this mean if I had DEXA on Hologic (-3.9), that I am taking Tymlos when I do not need it?
Ai said..... The slight difference between -3.9 and -3.3 is purely due to the fact that Lunar and Hologic use different reference groups and math formulas to calculate their scores—not because your bones are physically different.

I just asked Ai it said When we plug your actual BMD of 0.631 g/cm² into the cross-calibration formulas, here is how the numbers shift:Your Hologic Results: BMD of 0.631 g/cm² | T-score of -3.9Estimated GE Lunar Results (L4 Specific): BMD of 0.803 g/cm² | Estimated T-score of approx. -3.3Estimated GE Lunar Results (General Spine): BMD of 0.729 g/cm² | Estimated T-score of approx. -3.9Why You Still Have Osteoporosis. While an estimated Lunar T-score of -3.3 looks slightly "better" than a Hologic T-score of -3.9, it is crucial to look at where both numbers fall relative to the World Health Organization (WHO) diagnostic categories:Normal Bone Density: -1.0 or higher Osteopenia (Low Bone Mass): Between -1.0 and -2.5Osteoporosis: -2.5 or lower because both your actual Hologic T-score (-3.9) and your estimated Lunar T-score (-3.3 to -3.9) are significantly below the -2.5 threshold, your bone density is firmly in the osteoporosis range on both machines. The slight difference between -3.9 and -3.3 is purely due to the fact that Lunar and Hologic use different reference groups and math formulas to calculate their scores—not because your bones are physically different.

@summera1

I think of it like this that we have bone loss, and need to address it.

Theses machines while being the so call gold standard, can scare many people into starting medication when they might not yet need it. Add to it the lack of specialists in this area and its no wonder many question what to do next and feel concerned about the medication route. And then the overuse of prolia without explaining to patients the risks and the plan of following up with another medication to lock in gains.

@summera1 -3.3 is still a poor score. -3.9 is a really poor score. What would be questionable is if you had -3.0 on one machine and -2.5 on another, because -2.5 is not an automatic "must take meds" situation.

And even tho the tests I've had were on the same machine with the same technician, the area on the femoral neck was slightly larger on the current test than the previous test, making it look like a minor loss, but my rheumatologist caught the difference, did the math and said I had a 5.7% gain not a slight loss. Go figure. I think that as long as your T scores are trending down and your bone density is stable or trending up, and your TBS score is trending up, then you keep rocking it, carry on you Bone Warriors!

I wonder how I can find out which machine was used on me? It really doesn’t matter, I guess, since I break bones and don’t even realize it except fot some pain. When I broke my rib, I thought I just sprained a muscle. Still it would be nice to know.

@alidamc
Your DEXA report should note the machine that was used.

My doctors say a T-score of -2.5 means I must take medication. I started heavy weightlifting in April. My June DEXA showed a change from -2.4, where I had been for years, to -2.5. I’d been osteopenic for at least five years, yet no doctor ever mentioned lifestyle changes or the importance of preventing further bone loss. When I asked why no one raised concerns when I was at -2.4, my doctor said she had recommended weight-bearing exercise. I honestly don’t remember that or being warned about fracture risks. I wish someone had made the urgency clear years ago. But now I am questioning why go on a bone med when it is just such a slight difference? Earlier this year before diagnosis I started the weightlifting, stopped drinking alcohol (I was drinking way to much wine) and after the dexa I am now making sure I get in my protein. Going to discuss seeing where I am next April after the year of lifestyle changes versus starting Reclast right now.

@pennyskip Dr. Keith McCormick, author of "Great Bones", probably would not recommend medication for someone like you. He is not anti-medication, but thinks it is best used when T-scores get bad (i.e. in the -3 range.)

You are on the borderline between osteoporosis and osteopenia. I think you can certainly see what happens over the next year. If your T-scores continue to deteriorate, then you can conclude that what you're doing isn't working.

Have your hormone levels checked if you haven't already. Make sure your vitamin D3 level isn't low, and take a supplement if needed. Many people also take vitamin K2. Some use collagen peptide powder daily. Throw everything at the problem!

Holy Cow, Thanks! I just saw the original post about different test results with 2 different machines. I had no idea, and if you didn't post this I would never have known. So maybe I should ask some of my doctors about this and which technology I should rely on. It makes a difference in diagnosis and treatment, as I see written here, and for me it means which provider I should choose -- the overpriced one owned by the hospital (which has very good blood and imaging services, but unaffordable) or the other one most choose when they know the pricing schedules. The private standalone imaging center charges much less and there is no wait time. The hospital imaging is expensive and the DEXA wait time was 5-6 months, and this was unadvisable for someone who had so much pelvic radiation for cancer treatment.
What I didn't know about DEXA scans - they score 3 elements, not necessarily the ones most likely to fracture, so it's generic, not specific to cancer patients with pelvic radiation. Sacrals and lumbar 5 are not scored. Pubic bone isn't scored. It doesn't mean it isn't seen on the image, but the radiologist doesn't identify anything about those other elements or include them in the scoring.
But knowing there's a difference in machines and diagnosis tells me I need to ask the docs some questions about my next scan and where I need to have it done. Thanks!