Stiffness index identifies patients with osteoporotic fractures better than ultrasound velocity or attenuation alone
Introduction
Over the past decade several non-invasive techniques based on the attenuation of radiation have been developed to quantify bone mineral density (BMD) in the axial and peripheral skeleton [1], [2], [3]. Dual energy X-ray absorptiometry (DXA) and quantitative computed tomography (QCT) are standard methods. These techniques are important because they predict the risk of future osteoporotic fractures [4]. However, both DXA and QCT can be costly, involve exposure to radiation, and are not readily accessible.
Quantitative ultrasonometry (QUS) of the os calcis is another method of providing information on BMD and on bone quality [5], [6], [7], [8], [9]. Numerous retrospective studies, and several prospective studies have shown that os calcis QUS predicts osteoporotic fracture [10], [11], [12], [13], [14], [15], [16], [17], and in fact is as sensitive as DXA for risk of femur fracture [16], [17].
This cross-sectional study was designed to determine the value of these QUS variables of post-menopausal women with and without a history of osteoporotic fracture. In addition we investigated the age related decline of the ultrasound variables.
Section snippets
Material and methods
A cross-sectional sample of 1217 women was recruited during routine gynecological check up at the Hamburg Institute for Endocrinology and Reproductive Medicine and the Department of Gynecology at the University of Marburg. There were 741 post-menopausal women (59.2=7.8 years) and 476 normal pre-menopausal women who averaged almost 14 years younger. The postmenopausal women were further subdivided into 583 cases with ‘normal’ BMD (above T−2.5), those with low BMD (below T−2.5) without fracture (n
Age-related decline in ultrasound variables
Almost no age dependent decline was seen in the pre-menopausal women. BUA, SOS, and SI in healthy post-menopausal women were 10.4%, 2.4%, and 21.2% lower, respectively, than in women with low spine BMD. In women with fracture compared with healthy post-menopausal women these variables were even lower 13.7%, 2.7%, and 25.7% respectively for attenuation, velocity, and stiffness index.
ROC analysis of ultrasound variables
Table 1 gives the mean, standard deviation (S.D.), coefficient of variation (CV%) and standardised coefficients of
Discussion
Numerous cross-sectional and prospective studies have quantified BMD using DXA or QCT. However, these X-ray methods are costly and not widely available. QUS of the os calcis is a radiation-free, low-cost, rapid, and easily-used technique for evaluating BMD and predicting the risk of fracture. QUS not only measures BMD, but may provide incremental information on future risk [14], [16], [17]. Many cross-sectional, and some prospective studies on QUS and fracture risk have already been reported
Conclusion
Our results using ROC analysis showed that the SI is a better discriminator of women with osteoporosis either with or without a history of osteoporotic fracture than SOS or BUA alone. If these results can be confirmed in prospective longitudinal as well as in further cross-sectional studies, SI may prove a clinically useful tool in the diagnosis of a disorder that is becoming increasingly prevalent and important as populations age.
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