COMPARISON OF HIGH RESOLUTION PERIPHERAL QUANTITATIVE COMPTERIZED TOMOGRAPHY (HR-pQCT) WITH DUAL ENERGY X-RAY ABSORPTIOMETRY (DXA) FOR MEASURING BONE MINERAL DENSITY (BMD)

OBJECTIVE: was to compare the measurement of areal bone mineral density (aBMD) by dual energy X-ray absorptiometry (DXA) with the measurement of volumetric bone mineral density (vBMD) by high resolution peripheral computerised tomography(HR-pQCT) in subjects with a wide range of body mass indices (BMI). SUBJECTS: We scanned the arms and legs of 49 premenopausal women, aged 21-45, with BMI from 18.5-46.5, by high resolution peripheral computerized tomography (HR-pQCT) and found that there was a non-significant change in volumetric BMD (vBMD) associated with increased BMI whereas aBMD (DXA) was associated with a positive significant increase. HR-pQCT scans a slice at the extremity of the tibia and radius, whereas DXA scans the entire leg and arm. RESULTS: The correlation coefficients (r) of BMD (DXA) of the legs with BMI were 0.552 p<0.001, % Fat 0.378, p<0.01, and W 0.633, p<0.001. The r of BMD (DXA) of the arms with BMI 0.804 p<0.001, with % Fat 0.599 p<0.001, and with W 0.831 p<0.001 whereas the r of the average bone density (D 100) of legs and arms measured by HR-pQCT with BMI, W, and % Fat, were not significant. CONCLUSIONS: Although HR-pQCT and DXA scan different parts of the bone, the high r of BMD with BMI and low r of bone density measured by HR-pQCT with BMI suggests that BMD measured by DXA is artifactually increased in the presence of obesity.