Bone Density Tests: DEXA vs. REMS Explained
DEXA and REMS use different techniques to measure bone density.
A friend came to me quite worried that a recent REMS bone density test showed a drop in level from the results of her DEXA two years ago. According to the REMS, she had declined from osteopenia into osteoporosis. While waiting to get her two-year follow up DEXA, we investigated a comparison of the two measures of bone density. (Read to the bottom of the article for her ultimate results).
Key points to consider when comparing bone density tests
When comparing the reliability of assessing bone mineral density (BMD) between Dual-Energy X-ray Absorptiometry (DEXA) and Radiofrequency Echographic Multi-Spectrometry (REMS), there are some key points to consider in terms of:
Technology differences
Reliability and accuracy
Safety and convenience
Clinical use guidelines
Technology Differences
DEXA: Uses low-dose X-ray to measure BMD, primarily at the hip and spine. It provides a precise BMD measurement and is considered the gold standard for diagnosing osteoporosis and assessing fracture risk.
REMS: A newer, non-ionizing technique using ultrasound at specific bone sites (typically lumbar spine and femoral neck). REMS measures the bone’s echo frequency spectrum to calculate BMD without radiation exposure. Echolight is the name of the ultrasound device.
Reliability and accuracy
DEXA: High reliability, with standardized scoring (T-score and Z-score) widely used in osteoporosis diagnosis and treatment guidelines. Results are highly reproducible, especially in the same device or facility. DEXA can assess bone density changes over time, making it useful for monitoring treatment effects.
DEXA provides highly accurate BMD values but lacks insight into the bone’s internal structure and resilience.
REMS: Initial studies show that REMS is comparable in accuracy to DEXA, particularly in lumbar spine and femur measurements. However, its accuracy may vary based on technician experience and patient factors. The REMS device depends on ultrasound signals which can be affected by body composition and tissue density (e.g. obesity, extreme thinness, or significant bone deformities), though it has shown promising results in clinical trials.
The ultrasound echoes provide an estimation of bone quality beyond mineral density. The quality of the bone determines its “fragility score” which includes elements of the bone’s microstructural resilience, elasticity, and strength that contribute to its ability to withstand fractures.
3. Safety and convenience
DEXA: Although it uses low levels of radiation, there is still exposure to X-rays, which may be a concern for some patients, especially with repeated scans over time. However, DEXA is non-invasive, fast, and widely available in medical facilities. The scan is quick (typically 10–20 minutes), but the machine is often stationary, requiring the patient to visit a specialized facility.
REMS: REMS does not involve radiation, which is a significant safety advantage, especially for patients needing frequent monitoring (e.g., those on osteoporosis treatment). REMS is also portable, meaning it can be performed in various settings, including clinics or even at the bedside, which adds convenience. However, REMS is a relatively new technology and may not be as widely available as DEXA.
4. Clinical use and guidelines
DEXA: Since DEXA has long been the standard, most osteoporosis guidelines are based on DEXA-derived T-scores. It remains the most commonly used tool in clinical practice for BMD assessment and osteoporosis diagnosis.
REMS: Though promising, REMS is still gaining traction and isn’t as widely incorporated into guidelines. Research supports its efficacy, but more studies and guideline updates may be needed before it becomes a standard alternative to DEXA.
How to avoid confusing test results
In my friend’s case, it was not accurate to compare DEXA and REMS test results. She waited for a follow-up DEXA which showed that her BMD levels were still in the osteopenic category. In general, it is not viable to compare the results of the two different types of tests, as in comparing apples to oranges.
DEXA is currently the more established method, providing highly accurate BMD values, with extensive research backing its use and integration into clinical guidelines. It remains the most validated and trusted option in guidelines due to its robust data across all populations.
REMS offers BMD measurements in a way comparable to DEXA (though it might underestimate or overestimate in some cases) while providing indirect information about bone quality and its resistance to fracture. REMS offers a radiation-free, portable alternative, making it particularly advantageous for patients requiring frequent BMD assessments, though it’s still emerging in clinical practice.
Disclaimer: The information presented in this article should not be construed as medical advice. It is not intended to replace consultation with your physician or healthcare provider.
For related articles: Bone Density Test – Why It’s Important and What It Means; Osteoporosis Screening and Do You Need One?
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Joan Pagano is the author of best-selling fitness books, including the new release Strength Training Exercises for Women (DK, 2014), an informational speaker on health and fitness topics and the owner of Joan Pagano Fitness in New York City. Former trainer to Jacqueline Onassis and Caroline Kennedy, Joan has specialized in strength training for women since 1988. She is an authority on the benefits of exercise for women's health issues such as menopause, osteoporosis and breast cancer, as well as strength training through the decades. Joan is the proud finisher of seven marathons and a member of the Shaker Heights High School Alumni Hall of Fame.
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