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Accuracy of DEXA Scans
I am guessing that I am not the only one facing a medication decision based on one DEXA scan with no fractures. That raises the question as to how much reliance we should put on that single measurement. I trust that sites calibrate the instruments according to the manufacturer's specifications. But we read about the importance of proper positioning. I was only asked to lie on a table with no special consideration of position. Does improper position make bones appear denser or less dense? Or is the effect minimal?
Remember the old weight charts that had ideal weight ranges by height and bone structure? Does DEXA factor in bone structure when calculating density. Obviously, there is less bone for the x-rays to penetrate for a fine-boned person than for a heavy-boned one. That could be interpreted has having less bone mineral density which may not be the case.
Any insight or other pertinent questions?
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HugInterested in more discussions like this? Go to the Osteoporosis & Bone Health Support Group.
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@babs10 I don't think it takes into account your quality of bone. Which very important to determine frax risk.
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1 Reaction@awfultruth Could you confirm my understanding about what you are saying about post-treatment monitoring? I understand you are saying that monitoring might be done with bone markers? Is this what you are doing?
This is what I would like to do but not seeing this approach is in wide use so that I might have support to discuss with my PCP for ordering the tests.
Thanx for your thoughts....
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1 Reaction@rjd If you do a search on: mayoclinic ctx p1np
you will find several discussions of BTM Bone Turnover Markers.
Here is an example thread with posts from this year, but there are several others, including ones posted by me:
https://connect.mayoclinic.org/discussion/bone-marker-tests-ctx-and-p1np/
@rjd Hi there, yes, I am doing my own tracking of blood markers. After successfully taking Evenity for a year I switched to monthly Risedronate. In order to know if Risedronate was holding my Evenity gains I did a number of CTX and a couple of P1NPs to see what was happening with my bone resorption primarily. I did monthly CTX tests for 3-4 months , 1 before and several after starting the Risedronate. In my case I saw that the CTX stayed down below 300 for about two weeks but by 4 weeks it was climbing to 350-400. I considered that to be too high a CTX reading for keeping my bones. I started taking the monthly Risedronate every two to three weeks after seeing that pattern.
Unfortunately I did not maintain that level of thoroughness due to various life events. Though I did continue to do the CTX tests it became less consistent. But also logical that after I saw the pattern I did not need to test as often. 15 months later at my next DXA and TBS my readings had improved. Unfortunately one of the life events included me moving across country from the DXA machine I had been tested on for years. So the next (recent scan) was a different machine, different maker, different technician. So can't compare before and after the Risedronate as well as I would like. But the numbers being better makes it unlikely that they would be worse if I had measured on the same machine again. I conclude I either gained more on Risedronate or at worst lost only a little.
Now I've stopped Risedronate due to needing dental implants. I will resume tracking CTX and P1NP to help gauge whether I'm in the right condition for implants. And that I'm not losing rapidly after stopping the Risedronate. Not claiming any of this is exact and certain but it's one of the only ways I know of to help make best guesses.
For instance if my CTX had gone up and stayed up despite the Risedronate i would have talked to my doctor about changing meds. As it was I knew pretty well that the Risedronate was working though not perfectly. I could relax knowing I wasn't losing my Evenity gains.
The total cost for each CTX test was $68 via Jason Health with the blood draw done at Quest. Jason Health was very easy to work with.
Good luck with your efforts!
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2 Reactions@dvargo You're right - it doesn't take bone quality into account.
A CTX blood test only measures the rate at which your bones are being broken down (bone resorption). It detects tiny fragments released into the bloodstream when old bone is removed. It is primarily used to monitor the effectiveness of osteoporosis treatments or to assess bone density loss in postmenopausal women.
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I am getting a REMS scan tomorrow. I have similar concerns about the DEXA. Besides the REMS you can get more frequently because there's no radiation. Of course insurance doesn't cover. I will let you know how it goes tomorrow. I would hold off on the medication. They are definitely pushing it.
@awfultruth thank you for the details.
We appear to have been on similar paths as to the use of biomarkers for tracking response to meds. My meds involved 2 injections of Prolia followed by Alendronate for rebound prevention.
Results of biomarkers taken during the almost 2 years of Alendronate use were encouraging but the DEXA scan was NOT, which showed I lost all of the gains from Prolia after 2 years.
My last biomarkers were still encouraging so I decided on a drug holiday. I had no confidence in the most recent DEXA result because of what I considered hasty and sloppy placement by the technician who had, 2 years previously, placed me with meticulous precision.
I want to use biomarkers to monitor during this drug holiday but my new PCP is not interested in prescribing for me. My insurance had covered the previous CTX and P1NP blood tests. I would like to convince my new PCP to consider a prescription.
Are you saying you are paying out of pocket for the CTX test? And are you including a P1NP test?
@kfhoz I thought I had reviewed all the Mayo Connect postings and discussions about bone turnover markers and did not want to take on the exhausting task of re-reading to find an answer to my very specific questions.
I must have missed the thread you cite from the end of January as it involves the issue I have: monitoring biomarkers while not actively on any meds.
I take breaks from Connect every so often as it can become exceedingly time consuming and repetitive.
Thank you.
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1 Reaction@rjd And you can't rely on the subject/title lines. You start reading a thread that goes off the rails with people introducing new topics that have nothing to do with the original post you were interested in and wanted to follow. I wish the admins/moderators would take such posts and put them into an appropriately titled new post.
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