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Test: Dual Energy X-ray Absorptiometry (DEXA)

Dual Energy X-ray Absorptiometry (DEXA) is a common method of testing bone density as described here.

Notes and comments

TECH

  • Legacy content
    • f282:

DEXA: Dual Energy X-ray Absorptiometry The most widely test used to screen for osteoporosis is a bone density test (densitometry) that uses an enhanced X-ray technology called dual-energy x-ray absorptiometry (DXA or DEXA). This is NOT the same as a bone scan, which relies on a radioactive injection to help detect areas of increased bone metabolism due to fracture, infection or tumors.

During a bone density test, a low energy source is passed over the body. Information evaluated by a computer allows an estimate of bone mass. This helps the doctor get an idea of bone strength, osteoporosis and risk of fracture.

The results of a DEXA bone density test are interpreted by a radiologist and and report is sent to the doctor who ordered the test. The results will have two scores or numbers.

Understanding the Scores (←-click here) Your T-score compares you to a young adult of your gender with peak bone mass. Any T-score larger than -1 is considered normal. The Z-score reflects the amount of bone you have compared to other people your same size, age and gender. This number is related to percentiles. Originally, only Z-scores were calculated, but when bone density machines became commercially available beginning in the 80's, T-scores were devised because different manufacturers could not agree on a standard measurement. You can read about calculating and interpreting both scores here.

Still confused about what DEXA scores mean - in simple terms? Read this from the NIH.

How to read DEXA reports There are step-by step directions on how to read DEXA reports in this tutorial.

Checking against previous BMD results to assess if the rate of loss has slowed may show the turnaround.. see also..

Problems With DEXA Scores The reproducibility of DEXA scores is frequently reported at 1-2 percent. That 1-2 percent is the average, but the range of reproducibility can vary as much as 7 percent. Variations come from changes in machine reading (using the same machine), technologists who are doing the test, and slight changes and body positioning, all of which can affect the end results. The most frequent source of error in repeat tests is patient positioning. The technology is limited because BMD is a two-dimensional image of a three-dimensional object.

A few more issues related to DEXA scores are covered in this Wikipedia article which says, inter alia, “It is important for patients to get repeat BMD measurements done on the same machine each time, or at least a machine from the same manufacturer. Error between machines, or trying to convert measurments from one manufacturer's standard to another can introduce errors large enough to wipe out the sensitivity of the measurments.”

This Medscape article (registration required, but it is free) reviews the uses and limitations of BMD measurements and the relationship between BMD and bone strength.

Other Techniques Other tests that are used to evaluate bone health include bone ultrasound (usually of the heel) and quantitative computed tomography (QTC) of the spine.

Further Information: Osteoporosis and Th1 illness Risk factors, BMD testing and other information

My 25-DThe vitamin D metabolite widely (and erroneously) considered best indicator of vitamin D "deficiency." Inactivates the Vitamin D Nuclear Receptor. Produced by hydroxylation of vitamin D3 in the liver. is low and/or my 1,25-DPrimary biologically active vitamin D hormone. Activates the vitamin D nuclear receptor. Produced by hydroxylation of 25-D. Also known as 1,25-dihydroxycholecalciferol, 1,25-hydroxyvitamin D and calcitirol. is high. Should I be concerned about osteoporosis?

Don't I need to take a calcium supplement to prevent osteoporosis?

Don't I need Vitamin D to prevent bone loss?

It is very important not to overdo exercise.. there are a range of motion exercises within the Exercise guidelines FAQ.

A Review - Vitamin D and Calcium in Sarcoidosis (7-5-03) http://www.sarcinfo.com/calcium.htm

Meds to Avoid: When patients with an elevated level of 1,25-D are given Fosamax (or other biphosphanates), it can cause calcium deposition into the soft tissues, reduced organ function and possible osteonecrosis of the jaw (ONJ). All these meds have some effect on the immune or endocrine system and are, therefore, to be avoided.

  • s376:

What does my bone density test mean? (filelink)

DEXA: Dual Energy X-ray Absorptiometry The most widely test used to screen for osteoporosis is a bone density test (densitometry) that uses an enhanced X-ray technology called dual-energy x-ray absorptiometry (DXA or DEXA). This is NOT the same as a bone scan, which relies on a radioactive injection to help detect areas of increased bone metabolism due to fracture, infection or tumors.

During a bone density test, a low energy source is passed over the body. Information evaluated by a computer allows an estimate of bone mass. This helps the doctor get an idea of bone strength, osteoporosis and risk of fracture.

The results of a DEXA bone density test are interpreted by a radiologist and and report is sent to the doctor who ordered the test. The results will have two scores or numbers.

Understanding the Scores (←-click here) Your T-score compares you to a young adult of your gender with peak bone mass. Any T-score larger than -1 is considered normal. The Z-score reflects the amount of bone you have compared to other people your same size, age and gender. This number is related to percentiles. Originally, only Z-scores were calculated, but when bone density machines became commercially available beginning in the 80's, T-scores were devised because different manufacturers could not agree on a standard measurement. You can read about calculating and interpreting both scores here.

Still confused about what DEXA scores mean - in simple terms? Read this from the NIH.

How to read DEXA reports There are step-by step directions on how to read DEXA reports in this tutorial.

Problems With DEXA Scores The reproducibility of DEXA scores is frequently reported at 1-2 percent. That 1-2 percent is the average, but the range of reproducibility can vary as much as 7 percent. Variations come from changes in machine reading (using the same machine), technologists who are doing the test, and slight changes and body positioning, all of which can affect the end results. The most frequent source of error in repeat tests is patient positioning. The technology is limited because BMD is a two-dimensional image of a three-dimensional object.

A few more issues related to DEXA scores are covered in this Wikipedia article which says, inter alia, “It is important for patients to get repeat BMD measurements done on the same machine each time, or at least a machine from the same manufacturer. Error between machines, or trying to convert measurments from one manufacturer's standard to another can introduce errors large enough to wipe out the sensitivity of the measurments.”

This Medscape article (registration required, but it is free) reviews the uses and limitations of BMD measurements and the relationship between BMD and bone strength.

Other Techniques Other tests that are used to evaluate bone health include bone ultrasound (usually of the heel) and quantitative computed tomography (QTC) of the spine.

  • s378, s379:

Scientific studies

Polymorphisms at the ligand binding site of the vitamin D receptorA nuclear receptor located throughout the body that plays a key role in the innate immune response. gene and osteomalacia.

Calcium, Vitamin D Won't Protect Older Women From Fracture “At the same time, women taking calcium plus vitamin D experienced an increased risk for kidney stones, they added.”

……………………………….

Epidemiological study finds a strong association between high 1,25 D levels and osteoporosis. Relationships between bone mineral density, serum vitamin D metabolites and calcium:phosphorus intake in healthy perimenopausal women. Brot C, Jorgensen N, Madsen OR, Jensen LB, Sorensen OH.

The Danish epidemiologist Brot studied 500 healthy women ( that is they were not drawn from a population with particular health issues) aged 42 to 58 and concluded that in this group bone density was strongly inversely proportional to 1,25 D levels ( that is low bone density was strongly associated with high 1,25 D levels) and only rather weakly directly proportional to 25 D levels. The sample was chosen randomly - and was not done to test the impact of any particular treatment programme.

Last edited on Sun Jan 14th, 2007 20:00 by Meg Mangin R.N.

Belinda

Reply

Q: re Continued Bone Loss? I've been on the MP for over 1 and 1/2 years. When I started my D was 9.3 and 1,25 was 70. Now it's D 6.2 and 1,25 = 20.9. My doctor is now concerned that the levels are too low (under the normal range for 1,25) but also that my alk phosphate level has gone from 56 in 2003 to 134 now. A recent bone density scan has revealed significant oseoporosis and I have frequent broken ribs (hairline fractures) from doing nothing at all (like turning in bed).

I know the recommendation is against products like Boniva and Fosomax. I'm concerned, however that after a significant time there's been no improvement, but, in fact, continued bone loss.

Reply: from Belinda: Did you have actual bone density test numbers from pre-MP to compare with your most recent results?

The normal range of ALP, according to Medline is 20 to 140 IU/L, so your ALP is still within the normal range at 134. see further detail in FAQ What do my lab tests mean?

When my 1,25-D finally dipped below normal, I reminded my doc that getting 1,25-D was simple: just add a little light now and then. You could experiment to see if you could tolerate a little light exposure, like popping outdoors to move the water sprinkler in the late evening, when light rays are less direct. Remember to wear your sunglasses. Be on the lookout for how your body reacts to any increased light exposure, however brief.

The best way for normal people to induce bone building is to engage in weight-bearing exercise such as walking. For folks with Th1 - and dysregulated vitamin D, the first step to stronger bones is getting the elevated 1,25-D under control. So you are on the right path.

Sometimes the best answers are in non-drug interventions. Have you talked with your doctor the feasibility of beginning simple weight-bearing exercises with only a few repetitions, maybe every other day?

P.Bear R.N. reply: Your disease process helped cause these T scores, and the MP is the best thing you could possibly do to halt bone loss. It may also set your mind at ease if you read the book

The Myth of Osteoporosis: What Every Women Should Know About Creating Bone Health by Gillian Sanson An interview with her here:

http://www.womenshealthmatters.ca/resources/show_res.cfm?ID=42199\Womenshealth

Although she does not have our new information on “vitamin” D and does not understand that a low 25-D is most frequently associated with a high 1,25-D; she is generally on the right track.

You can see that test scores are not a good predictor of fracture. I hope your doc will continue to help you with the MP. best, P.B.

Meg Mangin R.N. Although you have lost bone density since your last bone scan, the rate of loss may have slowed. This was the case for me and my doctor was impressed. Check previous bone scans if possible and ask to be tested again after you've been on the MP longer.

http://www.marshallprotocol.com/forum39/8793-5.html

References

home/tests/dexa.txt · Last modified: 10.12.2018 by sallieq
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