Background: Calcaneal quantitative ultrasound (QUS) is widely used in osteoporosis screening, but the cut-off values for risk stratification remain unclear. This study validates the performance of a calcaneal QUS device (CM-200) using dual-energy X-ray absorptiometry (DXA) as the reference and establishes a new set of cut-off values for CM-200 in identifying subjects with osteoporosis.
Methods: The bone health status of Malaysians aged ≥40 years was assessed using CM-200 and DXA. Sensitivity, specificity, area under the curve (AUC) and the optimal cut-off values for risk stratification of CM-200 were determined using receiver operating characteristic (ROC) curves and Youden's index (J). Results: From the data of 786 subjects, CM-200 (QUS T-score <-1) showed a sensitivity of 82.1% (95% CI: 77.9-85.7%), specificity of 51.5% (95% CI: 46.5-56.6%) and AUC of 0.668 (95% CI: 0.630-0.706) in identifying subjects with suboptimal bone health (DXA T-score <-1) (p < 0.001). At QUS T-score ≤-2.5, CM-200 was ineffective in identifying subjects with osteoporosis (DXA T-score ≤-2.5) (sensitivity 14.4% (95% CI: 8.1-23.0%); specificity 96.1% (95% CI: 94.4-97.4%); AUC 0.553 (95% CI: 0.488-0.617); p > 0.05). Modified cut-off values for the QUS T-score improved the performance of CM-200 in identifying subjects with osteopenia (sensitivity 67.7% (95% CI: 62.8-72.3%); specificity 72.8% (95% CI: 68.1-77.2%); J = 0.405; AUC 0.702 (95% CI: 0.666-0.739); p < 0.001) and osteoporosis (sensitivity 79.4% (95% CI: 70.0-86.9%); specificity 61.8% (95% CI: 58.1-65.5%); J = 0.412; AUC 0.706 (95% CI: 0.654-0.758); p < 0.001). Conclusion: The modified cut-off values significantly improved the performance of CM-200 in identifying individuals with osteoporosis. Since these values are device-specific, optimization is necessary for accurate detection of individuals at risk for osteoporosis using QUS.
Keywords: bone; dual-energy X-ray absorptiometry; quantitative ultrasound; sensitivity; specificity.