FOREARM BMD AS MEASURED BY PERIPHERAL QUANTITATIVE COMPUTED-TOMOGRAPHY (PQCT) IN A GERMAN REFERENCE POPULATION

Low bone mass as estimated by decreased bone mineral density (BMD) is an established predictor of osteoporotic fractures. One of the latest developments in bone densitometry is peripheral quantitative computed tomography (pQCT) of the forearm. In Germany, the CT bone scanner XCT 900 has already been widely used; however, interpretation of measurements with respect to osteoporosis risk assessment can be improved by better defined and validated reference data. In the present study, this device was used to measure BMD at the distal radius in a well-defined healthy population of 179 German adults (91 men, 88 women) aged 20-79 years. In vivo precision was 1.67% for trabecular and 0.81% for total BMD measurements. Peak values of trabecular and total BMD were observed at the ages 40-50 years in women and 30-40 years in men. Beyond these ages, both trabecular and total BMD showed a linear decline with age, decreasing by 0.85% and 1.08% per year in women and by 0.59% and 0.54% in men, respectively. Measures of BMD were not influenced by weight, height or body mass index (BMI). In both sexes, trabecular and total radial BMD showed a positive and significant correlation with femoral BMD measures obtained by dual X-ray absorptiometry (DXA). Weaker correlations were observed with DXA measures of the lumbar spine. Compared with the 95% reference range provided by the manufacturer, the distribution of age- and sex-specific values of trabecular BMD of the distal radius was shifted to lower values by up to 1 standard deviation. Thus, 17% (30 of 179) of our apparently healthy population had BMD values falling short of the suggested lower reference limit. On the other hand, the distribution of total BMD values was shifted to higher values by up to 2 standard deviations in the younger age groups. We conclude that pQCT of the radius is a precise method for measuring BMD, but that its use for osteoporosis risk assessment crucially depends on both well-defined reference data and the results of prospective studies.