Could Ultrasound Serve as an Early Bone Density Screening Tool?

Pam Harrison

March 18, 2019

A small study has suggested that ultrasound of the heel bone could be a reasonable alternative to dual-energy X-ray absorptiometry (DEXA) to distinguish individuals with low bone mineral density (BMD).

"Using ultrasound to scan the heel won't give us all the information we could gather with a full DEXA scan," lead author Carolyn Komar, PhD, associate professor of biomedical sciences, West Virginia School of Osteopathic Medicine, Chicago, Illinois, said in a statement from her institution.

"However, it gives us a clear enough snapshot to know whether we should be concerned for the patient," she added.

The study was published in the March 2019 issue of the Journal of the American Osteopathic Association.

However, Nelson Watts, MD, director of Mercy Health Osteoporosis and Bone Health Services in Cincinnati, Ohio, told Medscape Medical News that the concept of using ultrasound as an initial screening tool for osteoporosis has been around since the mid-1980s, "so you have to wonder why ultrasound hasn't taken off, if researchers had uncovered some sort of secret."

And the current study, he says, "is deeply flawed," starting with the type of ultrasound machine used, which was about 20 years old, as well as the study population and design.

A Cheap, Widely Available Method of Screening Bones

Komar and colleagues explain that although DEXA is considered the gold standard to identify individuals with low BMD, its use is limited because of the cost and size, as well as the technical requirements to operate such a machine. Patients are also exposed to ionizing radiation, albeit at very low levels.

"Therefore, use of DEXA limits the ability to screen large populations for bone quality," they stress

Using ultrasound as a screening method will permit large populations to be assessed for bone quality with the hope that accessible early detection will enable interventions to occur before BMD is lost to a critical level, they note.

"Ultrasonography's lower cost, reduced technical needs, and low risk to patients facilitates the practice of preventive medicine in primary care settings," they add.

So the researchers set out to establish data ranges from calcaneus ultrasonography that correspond to BMD stratification identified by DEXA in 99 participants who agreed to heel ultrasound alone or plus a DEXA scan.

An Achilles bone ultrasonometer (GE Healthcare) was used to assess the density of the calcaneus. Once one foot was placed in the cradle of the machine, BMD T and Z scores were calculated and the procedure was repeated on the other foot. DEXA was then performed on the spine and left and right femurs, and T and Z scores were computed and recorded.

A DEXA BMD T score of the spine < −1.0 was defined as poor BMD and a score ≥ −1.0 was defined as good BMD.

Investigators then compared T scores for both the left and right foot measured by ultrasound with the T score from the DEXA scan of the spine for each participant.

"Ultrasonography readings of either the left or right foot were predictive of good versus poor bone quality," they report.

The study established an ultrasound BMD T score > 1.05 of the right heel as a potential indicator of good bone health, whereas a BMD T score < −1.05 indicated poor bone health.

"The ultrasound BMD T score was chosen as the evaluator of bone health because the diagnosis of osteoporosis is determined by a DEXA," they note.

"Ultrasonography of the calcaneus offers a low cost, efficient means to screen bone health. The affordability and mobility of an ultrasound machine enable its use as a screening method that may be applicable to large numbers of people," extending the assessment of BMD well beyond postmenopausal women, they say.

For example, more men could be screened, as well as younger people, to see if there is proper bone deposition during a period when lifestyle modifications could potentially improve BMD.

Study Limitations

Watts said study limitations were they enrolled only 99 patients, both men and women, with a median age of 65 years, although ages ranged from 27 to 94 years.

Importantly, individuals already scheduled for DEXA participated in the study, suggesting many already had suspected low BMD, another study weakness the authors acknowledge.

And participants included those taking glucocorticoid therapy, known to adversely affect bone health, those with rheumatoid arthritis, and those already on treatment for osteoporosis.

Watts also pointed out that the International Society of Clinical Densitometry — which he has been involved with for years — long ago recommended that any ultrasound device must have a device-specific threshold to be able to detect 90% of individuals who have osteoporosis as defined by gold standard DEXA measurements at the spine and hip.

"If you are going to find out where that study cut-point is, you would want to start with the general population, you would not mix up men and women, you would not mix up young and old people, you wouldn't take people who are on treatment for osteoporosis and you probably wouldn't take people who have rheumatoid arthritis either," he explained.

"And you probably would want to test at least 1000 people, and ideally, you would do a prospective study to see what your baseline measurements tell you as far as [future] fracture risk is concerned," he concluded.

The authors and Watts have reported no relevant financial relationships.

J Am Osteopath Assoc. 2019;119:147-154. Full text

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