2005, Number s1
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ABSTRACTObjective. To estimate the best cut-off point of bone mineral density (BMD) measured simultaneously by dual X-ray absorptiometry (DEXA) and quantitative computed tomography (QCT) to rule out vertebral compression fractures and determine the prognosis. Material and methods. Twelve females with vertebral fractures and 27 with no fractures were included. BMD was measured in both groups by DEXA and QCT. Results. In women with fractures, DEXA and QCT matched in classifying 9 patients with severe osteoporosis but with very different BMD averages (p = 0.0001). The other 3 were classified as osteopenic by DEXA and as severely osteoporotic by QCT (p = 0.0001). Of the 27 patients with no fractures, 21 were considered as normal; of the remaining 6 patients, one was classified by DEXA as normal while QCT classified her as having osteopenia; and 5 patients were considered by DEXA as osteopenic while QCT classified them as osteoporotic (p = 0.0001). The best cut-off point to simultaneously improve the sensitivity and specificity of DEXA and QCT, according to the ROC curves, would be 0.7705 and 0.6515 g/cm2, respectively. When applied in parallel, these values increased the sensitivity from 83.3% to 91.7% in detecting women at high risk of vertebral compression fracture, compatible with bone brittleness. Conclusions. 1. When the purpose is to discriminate and predict the presence or absence of fracture risk, the case classification (normal, osteopenic, osteoporotic, or severely osteoporotic) based on the BMD T-Score measured by DEXA does not accurately match the middle BMD levels of the vertebral bodies in our sample. 2. We recommend using both diagnostic procedures. While one measures the cortical BMD the other measures the trabecular BMD. Together, both are capable of more accurately classifying cases to predict the risk of vertebral compression fracture.
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