REMS T-Score (Left Femur)

Bone loss often causes no symptoms before a fracture. REMS estimates bone density using ultrasound, and this result describes the femoral neck of your left hip. Lower scores have been associated with future fractures in women, but the result needs to be considered with your age, fracture history, medications, and risk of falling.

REMS stands for Radiofrequency Echographic Multi Spectrometry. It is an emerging method with published reference data and prospective fracture studies. Its clinical evidence is less established than that of DXA, the low-dose X-ray method used in most osteoporosis treatment and monitoring guidelines. Agreement between the methods varies considerably across populations.

What the Score Measures

A probe over your hip sends ultrasound pulses toward the bone. Software analyzes the returning signals, rejects signals it identifies as unsuitable, and compares the remaining patterns with reference profiles. The resulting bone mineral density estimate is used to calculate the T-score. Age and body size also influence the calculation.

The femoral neck is the narrow stretch of thigh bone below the ball of the hip joint. A more negative T-score indicates lower estimated density relative to the young-adult reference. It describes relative density, which is one contributor to bone strength; it cannot establish how much bone you have personally lost without previous measurements.

Predicting a Broken Bone

A prospective study followed 1,370 women for an average of 3.7 years after REMS and DXA scans. About 14% experienced a fragility fracture. These fractures occur after a minor fall or other force that healthy bone would usually withstand.

In an age-matched analysis, women classified as having osteoporosis by femoral REMS had nearly three times the odds of a subsequent fracture. DXA classification performed similarly. But REMS classification identified only about 40% of the women who later fractured. A density result alone leaves substantial fracture risk unexplained, including risk related to previous fractures, falls, and steroid treatment.

REMS can also produce a separate Fragility Score from the ultrasound signal. A five-year study in women found that combining this score with the T-score improved fracture-risk discrimination compared with the T-score alone. That finding supports the combined assessment. The Fragility Score is a separate estimate of skeletal fragility, and its performance should not be attributed to this left-femur T-score by itself.

How It Lines Up With a DXA Scan

A European multicenter study enrolled 4,307 women. Among femoral scans retained after technical quality checks, REMS identified 90.4% of DXA-defined osteoporosis cases and correctly classified 95.5% of those without DXA-defined osteoporosis. Performance was less favorable when technically problematic scans were included, so those headline figures depend partly on scan acquisition and quality review.

A meta-analysis of 17 studies included femoral measurements from 7,464 people. REMS and DXA density estimates were strongly correlated, with a correlation of about 0.82, but results differed substantially between studies. Correlation describes how well measurements rise and fall together across a group. Two methods can correlate strongly while giving meaningfully different results for an individual.

A separate Australian study of 69 people attending a hospital clinic also found poor agreement for individual measurements. These findings limit the claim that REMS can routinely replace DXA, even when average results across larger groups look similar.

Why Scans Can Disagree

Some structures can make DXA density look higher than the underlying bone warrants. Arthritis-related bony growths, calcification of the abdominal aorta, and compressed vertebrae are especially relevant to lumbar-spine DXA. Studies suggesting that REMS avoids some of these effects have often focused on the spine. They do not establish that a lower left-femur REMS result is necessarily more accurate.

Type 2 diabetes creates a different problem: fracture risk can be elevated despite genuinely normal or higher bone density. This is a limitation of density as a complete measure of strength, rather than necessarily an error in the DXA measurement. Differences between REMS and DXA in diabetes do not, by themselves, establish which result better represents your fracture risk.

Hip Density and Lifespan

Low hip density is also associated with poorer survival in older adults. In a study of 5,823 US adults aged 60 and older, femoral-neck osteoporosis was associated with a roughly 73% higher rate of death in men and a 35% higher rate in women after adjustment for several health and lifestyle factors. These were DXA measurements, so this is indirect evidence for a REMS result. The association does not establish that low density caused the deaths or that raising a REMS score extends life.

Conditions That Thin the Hip

Bone is continually renewed as old tissue is removed and new tissue is formed. Bone loss develops when removal exceeds replacement. Several conditions can contribute, although most evidence connecting them to hip density comes from DXA studies.

• Menopause: falling estrogen levels speed bone breakdown and contribute to bone loss.
• Celiac disease: impaired nutrient absorption and inflammation can contribute to low density, including in men and premenopausal women.
• Lupus and kidney disease: inflammation, hormonal and mineral disturbances, and some treatments can contribute to skeletal fragility. Kidney transplant recipients can also have persistent bone disease.
• Inherited bone disorders: osteogenesis imperfecta affects the material that gives bone its structure. Both REMS and DXA studies have found low density in affected adults, but density alone does not capture the full extent of their bone fragility.

When Results Can Be Misleading

The ultrasound signal is only part of the calculation. Entered demographic information also affects the result, which matters when interpreting both a single scan and a change over time.

• Age and weight entries: in an experiment involving five healthy volunteers, entering an age ten years older lowered femoral-neck density estimates by about 6.3%, while entering a weight 5 kg higher raised them by about 4.3%. These changes occurred without a biological change in bone. The percentages describe the density estimate, not percentage changes in the T-score.
• Demographic dependence: a study of 209 adults found that age and weight explained more than 90% of variation in REMS density estimates. Accurate entries are necessary, but a change associated with aging or weight change still requires careful interpretation.
• Scan quality: probe position, depth, focus, and selection of the bone region affect the result. Software rejection of unsuitable signals does not eliminate acquisition errors.
• Spinal cord injury and altered anatomy: REMS can overestimate density in people with disuse-related bone loss. A reassuring result in this setting may miss clinically important fragility.
• Switching methods: a difference between REMS and DXA, or between different skeletal sites, cannot be interpreted as bone gained or lost.

Tracking Your Trend

Short-term repeatability is promising. In a study with 37 participants undergoing hip scans, the reported density precision error was about 0.32% for repeat measurements by one operator and 0.51% between operators. Those figures describe tightly controlled repeat scanning. They are not a universal rule for deciding whether an individual's bone has changed over a year.

A useful trend requires comparable scans and an understanding of the clinic's measurement variability. Changes in body weight, entered information, positioning, and software can complicate interpretation. The underlying density estimate and the T-score should also be kept distinct: density changes can be expressed as percentages, while T-score changes are expressed in points.

Small treatment-monitoring studies are beginning to report changes detected by REMS. Most evidence connecting treatment-related density changes to fracture prevention still comes from DXA and fracture outcomes, so REMS monitoring has a less established clinical role.