Comparison of a simple clinical risk index and quantitative bone ultrasound for identifying women at increased risk of osteoporosis

Abstract

Osteoporosis is a growing problem in Asia, and early identification of at risk subjects for preventive measures is likely the most cost-effective method for managing this disease in developing countries. Patients with low bone mineral density (BMD) have a high risk of future fracture. However, access to BMD measurements is limited in many areas of Asia, and inexpensive methods of targeting high-risk patients for BMD measurements would be valuable. We compared two methods, a simple clinical risk assessment tool, the Osteoporosis Self-assessment Tool for Asians (OSTA), and quantitative bone ultrasound (QUS) in identifying subjects with low BMD by DXA in 722 southern Chinese postmenopausal women recruited from the community in Hong Kong. Using the published cutoff value of -1 (versus 0 or higher) for OSTA to identify subjects with femoral neck BMD T-score ≤ -2.5, basing on our local population peak young mean value, the sensitivity and specificity was 88% and 54% respectively. The optimal cutoff T-score of -2.35 for QUS yielded sensitivity and specificity values of 81% and 65%, respectively. The AUC for QUS was 0.78, which was not significantly different from that of 0.80 for OSTA. Both OSTA and QUS correlated significantly with BMD at the femoral neck (0.62 and 0.36, respectively, P both < 0.001). When these cut-off values were used to identify subjects with either lumbar spine or femoral neck BMD T-score ≤ -2.5, the sensitivity and specificity was 79% and 60%, respectively, for OSTA, and 69% and 70%, respectively, for QUS. Combining QUS with OSTA improved the sensitivity to 91%, but the specificity was reduced to 44%. We conclude that the simple clinical risk assessment tool OSTA is a free and effective method for identifying subjects at increased risk of osteoporosis, and its use could facilitate the appropriate and more cost-effective use of bone densitometry in developing countries.