Ultrasonographic Stiffness Index May Help Determine Osteoporotic Fracture Risk

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Ultrasonographic Stiffness Index May Help Determine Osteoporotic Fracture Risk CME

News Author: Laurie Barclay, MDCME Author: Vega, MD Disclosures

Laurie Barclay, MDDisclosure: Laurie Barclay, MD, has disclosed no relevant financial relationships.

Vega, MDDisclosure: Vega, MD, has disclosed an advisor/consultant relationship to Novartis, Inc.

Brande Disclosure: Brande has disclosed no relevant financial information.

June 27, 2008 — A quantitative ultrasonographic stiffness index and 4 clinical risk factors may be used as an alternative to dual x-ray absorptiometry (DXA) to assess women at higher vs lower risk for osteoporotic fractures, according to the results of a study reported in the July issue of Radiology.

"Quantitative US [ultrasonography] of the heel is noninvasive, free of radiation, and relatively inexpensive; moreover, it helps predict fracture risk independently of DXA," write Idris Guessous, MD, from Lausanne University Hospital in Lausanne, Switzerland, and colleagues. "We hypothesized that a simple score incorporating clinical risk factors of osteoporotic fractures and bone status assessed by using quantitative US of the heel could be used to help predict the risk of osteoporotic fractures. Thus, the purpose of our study was to derive a prediction rule by using prospectively obtained clinical and bone US data to identify elderly women at risk for osteoporotic fractures."

Using data from a 3-year, prospective, multicenter study, the investigators computed a prediction rule to evaluate the predictive value of heel-bone quantitative ultrasonography in 6174 Swiss women 70 to 85 years of age. Factors considered in the predictive rule were the quantitative ultrasonographic stiffness index at the heel bone, baseline characteristics, and known risk factors for osteoporosis and fall. A univariate model was used to determine predictive values, and these were adjusted with multivariate analysis.

Five risk factors for the incidence of osteoporotic fracture were older age (> 75 years; P < .001), low heel-bone quantitative ultrasonographic stiffness index (< 78%; P < .001), history of fracture (P = .001), recent fall (P = .001), and failed chair test (P = .029). To calculate the score, points were assigned to these risk factors as follows: age, 2 (3 if age > 80 years); low quantitative US stiffness index, 5 (7.5 if stiffness index < 60%); history of fracture, 1; recent fall, 1.5; and failed chair test, 1.

For a high sensitivity of 90%, the cutoff value was 4.5. With this cutoff value, 1464 women were classified as lower risk for fracture (score, < 4.5) and 4710 were at higher risk (score, ≥ 4.5). Osteoporotic fracture occurred in 6.1% of the higher-risk women vs 1.8% of women at lower risk. Of women who had a hip fracture, 90% were in the higher-risk group.

"A prediction rule obtained by using quantitative US stiffness index and four clinical risk factors helped discriminate, with high sensitivity, women at higher versus those at lower risk for osteoporotic fracture," the study authors write.

Limitations of this study include suboptimal specificity of 23%, analysis not including women with secondary osteoporosis or women older than 85 years of age, and concerns regarding the score items themselves.

"Our prediction rule is a simple tool that can be applied systematically in the evaluation of elderly patients," the study authors conclude. "Moreover, integration of heel quantitative US parameters may be an effective alternative to DXA in response to the expected growth in demand for osteoporosis management in the next decades."

The Swiss Evaluation of the Methods of Measurement of Osteoporotic Fracture Risk study was funded by the Concordat des Caisses-Maladies Suisses. The study authors have disclosed no relevant financial relationships.

Radiology. 2008;248:179-184.

Clinical Context

Clinicians should consider screening older women for osteoporosis, and the method of choice for this screening is DXA. However, the availability of DXA is limited in many areas and may be insufficient to screen a growing community of older adults. An ultrasound examination can also provide results that independently predict the risk for future osteoporotic fracture in women, and it offers the advantage of low cost and no exposure to radiation vs DXA. In addition, ultrasound can provide data regarding bone architecture and elasticity. However, it is inaccurate in providing information regarding DXA-defined osteoporosis, and there is no universal treatment protocol to treat patients on the basis of ultrasound examination results.

Nonetheless, ultrasound may be applied to a larger number of adults in need of screening. The current study assesses the use of a heel-bone ultrasound examination along with a clinical screening tool to estimate the risk for future osteoporotic fracture.

Study Highlights

Researchers used data from the Swiss Evaluation of the Methods of Measurement of Osteoporotic Fracture Risk study. This study was designed to test algorithms to predict the risk for hip fracture among women aged 70 years or older. Women with a history of previous hip fracture, renal failure, dementia, or active cancer were excluded from study participation, as were those who were aged 85 years or older. All participants underwent a baseline history and physical examination, which emphasized fall risk. They completed a chair test to assess agility. Study subjects also had a heel-bone ultrasound examination, which was used to calculate a stiffness index of the calcaneus. The main outcome of the study was osteoporotic fracture, as defined by fracture of the wrist, hip, or arm after a low-grade traumatic injury. Researchers developed a survey instrument, which used the following factors to predict the risk for osteoporotic fracture:

Age older than 75 years Low heel-bone quantitative stiffness index (< 78%) History of fracture Recent fall Failed chair test (inability to rise from a chair 3 times in succession without using the arms)

The survey created a point scale from 0 to 14, with a higher score associated with a higher risk for fracture. 6174 women provided data for analysis. The mean age of subjects was 75 years, and the mean body mass index was 25.9 kg/m2. 52% of women had a history of previous fracture, and 31% had experienced a recent fall. 317 women experienced a fracture during follow-up. To obtain a 90% sensitivity to predict fracture, the authors used a cutoff score of 4.5 in the risk assessment. This meant that 76.3% of women were considered at high risk for osteoporotic fracture, whereas 23.7% of women were at low risk. Osteoporotic fracture occurred in 6.1% of high-risk women and in only 1.8% of low-risk women. The sensitivity of the screening tool was between 85% and 95%, whereas the specificity was between 21% and 25%. The sensitivity of a screening test for hip fracture specifically was even better than that for all osteoporotic fractures in general.

Pearls for Practice

An ultrasound examination can provide results that independently predict the risk for future osteoporotic fracture in women, and it offers the advantage of low cost and no exposure to radiation vs DXA. In addition, ultrasound can provide data regarding bone architecture and elasticity. However, there is no universal treatment protocol to treat patients on the basis of ultrasound examination results. The current study demonstrates good sensitivity for an assessment tool for osteoporotic fracture. The assessment tool includes data regarding advanced age, heel-bone ultrasound examination data, history of recent falls, history of fracture, and a chair test

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