Can the WHO criteria for diagnosing osteoporosis be applied to calcaneal quantitative ultrasound?

With the increasing number of quantitative ultrasound (QUS) devices in use worldwide it is important to develop strategies for the clinical use of QUS . The aims of this study were to examine the age-dependence of T-scores and the prevalence of osteoporosis using the World Health Organization Study G roup criteria for diagnosing osteoporosis and to examine the T-score thresh old that would be appropriate to identify women at risk of osteoporosis usi ng QUS. Two groups of women were studied: (i) 420 healthy women aged 20-79 years with no known risk factors associated with osteoporosis; (ii) 97 post menopausal women with vertebral fractures. All subjects had dual-energy X-r ay absorptiometry (DXA) measurements of the spine and hip and QUS measureme nts on three calcaneal ultrasound devices (Hologic Sahara, Hologic UBA575+, Osteometer DTUone). A subgroup of 102 (76 on the DTUone) healthy women age d 20-40 years was used to estimate the young adult mean and SD for each QUS and DXA measurement parameter to calculate T-scores. The age-related decli ne in T-scores for QUS measurement parameters was half the rate observed fo r the bone mineral density (BMD) measurements. The average T-score for a wo man aged 65 years was -1.2 for QUS measurements and -1.75 for the BMD measu rements. When osteoporosis was defined by a T-score less than or equal to-2 .5 the prevalence of osteoporosis in healthy postmenopausal women was 17%, 16% and 12% for lumbar spine, femoral neck and total hip BMD respectively. When the same definition was used for QUS measurements the prevalence of os teoporosis ranged from 2% to 8% depending on which ultrasound device and me asurement parameter was used. Four different approaches, based on DXA-equiv alent prevalence rates of osteoporosis, were utilized to examine which T-sc ore threshold would be appropriate for identifying postmenopausal women at risk of osteoporosis using QUS measurements. These ranged from -1.05 to -2. 12 depending upon the approach used to estimate the threshold and on which QUS device the measurements were performed, but all were significantly lowe r than the threshold of -2.5 used for BMD measurements. In conclusion, the WHO threshold of T = -2.5 for diagnosing osteoporosis requires modification when using QUS to assess skeletal status. For the three QUS devices used i n this study, a T-score threshold of -1.80 would result in the same percent age of postmenopausal women classified as osteoporotic as the WHO threshold for BMD measurements. Corresponding T-score thresholds for individual meas urement parameters on the two commercially available devices were -1.61, -1 .94 and -1.90 for Sahara BUA, SOS and estimated heel BMD respectively and - 1.45 and -2.10 for DTU BUA and SOS respectively Additional studies are need ed to determine suitable T-score thresholds for other commercial QUS device s.