Imaging ultrasonometry of the calcaneus: Optimum T-score thresholds for the identification of osteoporotic subjects

The purpose of the present study was to (1) examine the age dependence of T-score results for calcaneal imaging ultrasonometry and dual X-ray absorptiometry of the axial skeleton and (2) determine the optimum T-score thresholds appropriate for broadband ultrasound attenuation (BUA) and speed of sound (SOS) measurements. A total of 453 healthy women aged 20-79 years were included in the study. All study participants underwent bone mineral density (BMD) measurements of the lumbar spine, femoral neck, total hip and calcaneal measurements of the BUA and SOS. An imaging ultrasound device (UBIS, DMS, France) was used for the ultrasound measurements. T-scores were calculated using a subgroup of 71 healthy women aged 20-35 years to estimate the mean value of young normals and SD for BUA, SOS, and BMD. The age-related decline in both BUA and SOS T-scores was slower than that in the equivalent figures obtained by BMD measurements. The optimum T-score thresholds estimated by receiver operating characteristic (ROC) analysis were -1.3 for BUA and -1.5 for SOS. Using the optimum threshold, the sensitivity and specificity for BUA was 68% and 83%, respectively. Corresponding values for SOS were 63% and 79%. Utilizing calculated optimum T score thresholds for BUA and SOS, the agreement among BUA, SOS, and BMD at the femoral neck was improved compared with that found using the T-score of less than or equal to -2.5 criterion. In conclusion, the definition of osteoporosis by a T-score of less than or equal to -2.5 was not applicable to imaging ultrasonometry of the calcaneus. Optimum T-score thresholds were determined for both BUA and SOS suitable to Ubis QUS device.