Stiffness index identifies patients with osteoporotic fractures better than ultrasound velocity or attenuation alone

Objectives: To compare a composite ultrasonometry variable, the stiffness index (SI), with its two component variables of speed of sound (SOS) and broadband ultrasound attenuation (BUA), in identifying post-menopausal women with low bone mineral density (BMD) and/or osteoporotic fracture, Methods: A cross sectional sample of 1217 women (mean (S.D.) age 53.9 (9.7) years) was studied. Risk factors for osteoporosis were assessed by detailed questionnaire and women with diseases: or those taking treatments known to affect bone metabolism were excluded. Women were allocated to one of four groups: pre-menopausal women (n = 476), healthy post-menopausal women (n = 583), post-menopausal women with low BMD (n = 101), and post-menopausal women with osteoporotic fracture (n = 57). An Achilles ultrasonometer was used to perform quantitative ultrasonometry (QUS) at the os calcis. The SI, calculated mathematically from SOS and BUA, was computed. Results: Analysis of receiver operating curves (ROC) between healthy post-menopausal women and post-menopausal women with low BMD but no fracture, showed that the area under the curve (AUC) for SI was significantly greater than that for BUA (P < 0.001) or SOS (P < 0.05). For healthy post-menopausal women compared to women with fracture, the area AUC for SI was significantly greater than that for BUA (P < 0.05) or SQS (P < 0.001). No significant difference was found for AUC between BUA and SOS. Conclusion: QUS variables discriminated women with low density or fracture from healthy postmenopausal controls. The SI was a significantly better indicator than BUA or SOS in this retrospective study. (C) 1999 Elsevier Science Ireland Ltd. All rights reserved.